U.S. patent application number 13/255749 was filed with the patent office on 2012-02-02 for transparent conductive film and transparent conductive film laminated body and production method of same, and silicon-based thin film solar cell.
This patent application is currently assigned to Sumitomo Metal Mining., Ltd.. Invention is credited to Yoshiyuki Abe, Tokuyuki Nakayama.
Application Number | 20120024381 13/255749 |
Document ID | / |
Family ID | 42728400 |
Filed Date | 2012-02-02 |
United States Patent
Application |
20120024381 |
Kind Code |
A1 |
Abe; Yoshiyuki ; et
al. |
February 2, 2012 |
TRANSPARENT CONDUCTIVE FILM AND TRANSPARENT CONDUCTIVE FILM
LAMINATED BODY AND PRODUCTION METHOD OF SAME, AND SILICON-BASED
THIN FILM SOLAR CELL
Abstract
A transparent conductive film, useful in producing a highly
efficient silicon-based thin film solar cell, superior in hydrogen
reduction resistance and superior in optical confinement effect; a
transparent conductive film laminated body using the same; a
production method therefor; and a silicon-based thin film solar
cell using this transparent conductive film or the transparent
conductive film laminated body, as an electrode. It is provided by
a transparent conductive film or the like, characterized by
containing zinc oxide as a major component and at least one or more
kinds of added metal elements selected from aluminum and gallium,
whose content being within a range shown by the following
expression (1), and having a surface roughness (Ra) of equal to or
larger than 35.0 nm, and a surface resistance of equal to or lower
than 65 .OMEGA./.quadrature.
--[Al]+0.30.ltoreq.[Ga].ltoreq.-2.68.times.[Al]+1.74 (1) (wherein
[Al] represents aluminum content expressed as atomicity ratio (%)
of Al/(Zn+Al); while [Ga] represents gallium content expressed as
atomicity ratio (%) of Ga/(Zn+Ga)).
Inventors: |
Abe; Yoshiyuki;
(Ichikawa-shi, JP) ; Nakayama; Tokuyuki;
(Ichikawa-shi, JP) |
Assignee: |
Sumitomo Metal Mining.,
Ltd.
Tokyo
JP
|
Family ID: |
42728400 |
Appl. No.: |
13/255749 |
Filed: |
March 10, 2010 |
PCT Filed: |
March 10, 2010 |
PCT NO: |
PCT/JP2010/054004 |
371 Date: |
September 9, 2011 |
Current U.S.
Class: |
136/261 ;
204/192.29; 428/141 |
Current CPC
Class: |
H01B 1/08 20130101; H01L
31/0236 20130101; H01L 31/022483 20130101; C23C 14/0036 20130101;
H01L 31/1884 20130101; C04B 35/453 20130101; Y02E 10/50 20130101;
C04B 2235/3286 20130101; H01L 31/022466 20130101; Y10T 428/24355
20150115; H01L 31/02363 20130101; C23C 14/086 20130101; C04B
2235/3217 20130101; C04B 2235/3284 20130101 |
Class at
Publication: |
136/261 ;
428/141; 204/192.29 |
International
Class: |
H01L 31/0224 20060101
H01L031/0224; H01L 31/0264 20060101 H01L031/0264; H01L 31/02
20060101 H01L031/02; B32B 3/00 20060101 B32B003/00; C23C 14/34
20060101 C23C014/34 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 13, 2009 |
JP |
2009-061045 |
Claims
1. A transparent conductive film characterized by comprising zinc
oxide as a major component and at least one or more kinds of added
metal elements selected from aluminum and gallium, whose content
being within a range shown by the following expression (1) and
having a surface roughness (Ra) of equal to or larger than 35.0 nm
and a surface resistance of equal to or lower than 65
.OMEGA./.quadrature.
--[Al]+0.30.ltoreq.[Ga].ltoreq.-2.68.times.[Al]+1.74 (1) (wherein
[Al] represents aluminum content expressed as atomicity ratio (%)
of Al/(Zn+Al), while [Ga] represents gallium content expressed as
atomicity ratio (%) of Ga/(Zn+Ga)).
2. The transparent conductive film according to claim 1,
characterized in that haze ratio is equal to or higher than 8%.
3. The transparent conductive film according to claim 1 or 2,
characterized in that haze ratio is equal to or higher than
10%.
4. The transparent conductive film according to claim 1 or 2,
characterized in that haze ratio is equal to or higher than
16%.
5. The transparent conductive film according to claim 1,
characterized in that the surface resistance is equal to or lower
than 20 .OMEGA./.quadrature..
6. The transparent conductive film according to claim 1 or 5,
characterized in that the surface resistance is equal to or lower
than 15 .OMEGA./.quadrature..
7. A method for producing the transparent conductive film according
to claim 1 or 2 forming a zinc oxide-based transparent conductive
film (II) on a substrate, by a sputtering method, using an oxide
sintered body target comprising zinc oxide as a major component and
at least one or more kinds of added metal elements selected from
aluminum and gallium, characterized by performing film formation in
high speed, by setting a direct current input power density of
equal to or higher than 1.66 W/cm.sup.2 to the aforesaid oxide
sintered body target, under condition of a sputtering gas pressure
of 2.0 to 15.0 Pa, and a substrate temperature of 200 to
500.degree. C.
8. A transparent conductive film laminated body, characterized in
that the zinc oxide-based transparent conductive film (II)
according to claim 1 was formed on an indium oxide-based
transparent conductive film (I) formed on the substrate.
9. The transparent conductive film laminated body according to
claim 8, characterized in that the transparent conductive film (II)
is a crystalline film comprising a hexagonal crystalline phase.
10. The transparent conductive film laminated body according to
claim 9, characterized in that the hexagonal crystalline phase has
approximately c-axis orientation, and a c-axis inclination angle is
equal to or smaller than 10 degree, relative to a vertical
direction of a substrate surface.
11. The transparent conductive film laminated body according to
claim 8, characterized in that the indium oxide-based transparent
conductive film (I) is a crystalline film comprising indium oxide
as a major component and at least one or more kinds of metal
elements selected from Sn, Ti, W, Mo, and Zr.
12. The transparent conductive film laminated body according to
claim 8, characterized in that the indium oxide-based transparent
conductive film (I) comprises indium oxide as a major component and
Sn, whose content ratio is equal to or lower than 15% by atom, as
atomicity ratio of Sn/(In+Sn).
13. The transparent conductive film laminated body according to
claim 8, characterized in that the indium oxide-based transparent
conductive film (I) comprises indium oxide as a major component and
Ti, whose content ratio is equal to or lower than 5.5% by atom, as
atomicity ratio of Ti/(In+Ti).
14. The transparent conductive film laminated body according to
claim 8, characterized in that the indium oxide-based transparent
conductive film (I) comprises indium oxide as a major component and
W, whose content ratio is equal to or lower than 4.3% by atom, as
atomicity ratio of W/(In+W).
15. The transparent conductive film laminated body according to
claim 8, characterized in that the indium oxide-based transparent
conductive film (I) comprises indium oxide as a major component and
Zr, whose content ratio is equal to or lower than 6.5% by atom, as
atomicity ratio of Zr/(In+Zr).
16. The transparent conductive film laminated body according to
claim 8, characterized in that the indium oxide-based transparent
conductive film (I) comprises indium oxide as a major component and
Mo, whose content ratio is equal to or lower than 6.7% by atom, as
atomicity ratio of Mo/(In+Mo).
17. The transparent conductive film laminated body according to
claim 8, characterized in that the surface resistance is equal to
or lower than 20 .OMEGA./.quadrature..
18. The transparent conductive film laminated body according to
claim 8, characterized in that the haze ratio is equal to or higher
than 12%.
19. A method for producing the transparent conductive film
laminated body according to claim 8, characterized by firstly
forming a crystalline film of the indium oxide-based transparent
conductive film (I) on a substrate, by a sputtering method, using
an oxide sintered body target comprising indium oxide as a major
component containing at least one or more kinds of metal elements
selected from Sn, Ti, W, Mo, and Zr, and then forming the zinc
oxide-based transparent conductive film (II) on the indium
oxide-based transparent conductive film (I), by switching to an
oxide sintered body target comprising zinc oxide as a major
component and at least one or more kinds of added metal elements
selected from aluminum and gallium.
20. The method for producing the transparent conductive film
laminated body according to claim 19, characterized in that the
indium oxide-based transparent conductive film (I) is formed as an
amorphous film, under condition of a substrate temperature of equal
to or lower than 100.degree. C. and a sputtering gas pressure of
0.1 to 1.0 Pa, and subsequently crystallized by heat treatment at
200 to 400.degree. C.
21. The method for producing the transparent conductive film
laminated body according to claim 19, characterized in that the
indium oxide-based transparent conductive film (I) is formed as a
crystalline film, under condition of a substrate temperature of 200
to 400.degree. C. and a sputtering gas pressure of 0.1 to 1.0
Pa.
22. A silicon-based thin film solar cell, wherein the transparent
conductive film according to claim 1 or 2, or the transparent
conductive film laminated body according to claim 8 is formed on a
translucent substrate, and at least one kind of a unit selected
from one conducting type semiconductor layer unit, a photoelectric
conversion layer unit, and other conducting type semiconductor
layer unit, is arranged on the aforesaid transparent conductive
film or transparent conductive film laminated body, and a back
surface electrode layer is arranged on said unit.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a transparent conductive
film and a transparent conductive film laminated body and a
production method of same, and a silicon-based thin film solar
cell, and in more detail, relates to a transparent conductive film,
useful in producing a highly efficient silicon-based thin film
solar cell, superior in hydrogen reduction resistance and superior
in optical confinement effect; a transparent conductive film
laminated body using the same; a production method of same; and a
silicon-based thin film solar cell using this transparent
conductive film or the transparent conductive film laminated body,
as an electrode.
[0003] 2. Description of the Prior Art
[0004] A transparent conductive film having high conductivity and
high transmittance in a visible light region has been utilized in
an electrode or the like, for a solar cell or a liquid crystal
display element, and other various light receiving elements, as
well as a heat ray reflection film for an automotive window or
construction use, an antistatic film, and a transparent heat
generator for various anti-fogging for a refrigerator showcase and
the like.
[0005] As the transparent conductive film, there has been known a
thin film based on tin oxide (SnO.sub.2)-type, zinc oxide
(ZnO)-type, indium oxide (In.sub.2O.sub.2)-type. As the tin
oxide-type, one containing antimony as a dopant (ATO), or one
containing fluorine as a dopant (FTO) has been utilized. As the
zinc oxide-type, one containing aluminum as a dopant (AZO), or one
containing gallium as a dopant (GZO) has been utilized. The
transparent conductive film most widely used industrially is the
indium oxide-type, and among them, indium oxide containing tin as a
dopant is called an ITO (Indium-Tin-Oxide) film, and has been
utilized widely, because, in particular, a film with low resistance
can be obtained easily.
[0006] In recent years, problems of global environment caused by
increase in carbon dioxide, and price hike of fossil fuel have been
closed up, and a thin film solar cell producible at relatively low
cost has attracted the attention. The thin film solar cell
generally contains a transparent conductive film sequentially
laminated on a translucent substrate, one or more semiconductor
thin film photoelectric converting units, and a back surface
electrode. Because a silicon material is abundant in resource, the
silicon-based thin film solar cell using a silicon-based thin film
as the photoelectric converting unit (a light absorbing layer) was
practically used with extraordinary speed, among the thin film
solar cells, and research and development thereof has increasingly
been progressed actively.
[0007] And, kinds of the silicon-based thin film solar cells have
been diversified, and other than amorphous thin film solar cells
using an amorphous thin film such as amorphous silicon as a
conventional light absorbing layer, a micro crystalline thin film
solar cell using a micro crystalline thin film in which fine
crystalline silicon is present together in amorphous silicon, or a
crystalline thin film solar cell using a crystalline thin film
composed of crystalline silicon, has been developed, and also a
hybrid thin film solar cell obtained by laminating these has also
been practically used.
[0008] Here, the photoelectric converting unit or the thin film
solar cell in which the photoelectric converting layer occupying a
major part thereof is amorphous is called an amorphous unit or an
amorphous thin film solar cell, while one in which the
photoelectric converting layer is crystalline is called a
crystalline unit or a crystalline thin film solar cell, and one in
which the photoelectric converting layer is micro crystalline is
called a micro crystalline unit or a micro crystalline thin film
solar cell, irrespective of whether a p-type and n-type
conductive-type semiconductor layer contained therein is amorphous,
crystalline or micro crystalline.
[0009] It should be noted that, the transparent conductive film has
been used as a surface transparent electrode of the thin film solar
cell, and to efficiently confine light injected from the
translucent substrate side into the photoelectric conversion unit,
many fine irregularities are usually formed at the surface
thereof.
[0010] As an index representing degree of the irregularity of this
transparent conductive film, there is haze ratio. This corresponds
to one obtained by dividing scattering components, whose optical
pass is bent, with total components, among transmitting light, when
light of a specific light source was injected to the translucent
substrate with the transparent conductive film, and is measured
using usually a C light source containing visible light. Generally,
the higher elevation difference of the irregularity is made, or the
larger space between the concave part and the convex part of the
irregularity becomes, the haze ratio becomes the higher, and the
light injected into the photoelectric conversion unit is confined
efficiently, that is, what is called optical confinement effect is
superior.
[0011] Irrespective of whether the thin film solar cell is one
having amorphous silicon, crystalline silicon or micro crystalline
silicon as a single layer of a light absorption layer, or the
above-described hybrid-type one, high short circuit current density
(Jsc) can be attained, and the thin film solar cell with high
conversion efficiency can be produced, as long as sufficient
optical confinement can be performed by increasing the haze ratio
of the transparent conductive film.
[0012] From the above object, as the transparent conductive film
having high degree of the irregularity and high haze ratio, a metal
oxide material containing tin oxide as a major component, which is
produced by a thermal CVD method, has been known, and it has been
utilized generally as a transparent electrode of the thin film
solar cell.
[0013] A conductive-type semiconductor layer formed at the surface
of the transparent conductive film is generally produced by a
plasma CVD method, in gas atmosphere containing hydrogen. Raising
formation temperature to make micro crystal contained in the
conductive-type semiconductor layer results in promoting reduction
of a metal oxide with existing hydrogen, and in the case of the
transparent conductive film having tin oxide as a major component,
loss of transparency caused by reduction with hydrogen is observed.
Use of such a transparent conductive film with inferior
transparency cannot attain the thin film solar cell with high
conversion efficiency.
[0014] As a method for preventing reduction caused by hydrogen of
the transparent conductive film having tin oxide as a major
component, a method for forming thinly a zinc oxide film superior
in reduction resistance, by a sputtering method, on the transparent
conductive film composed of tin oxide with high degree of the
irregularity formed by the thermal CVD method, has been proposed
(NON-PATENT LITERATURE 1). There has been disclosed that
transparency of the transparent conductive film can be maintained
high by taking the above structure, because zinc oxide has strong
bonding between zinc and oxygen and is superior in hydrogen
reduction resistance.
[0015] However, because film formation should be performed by
combining two kinds of methods, to obtain the transparent
conductive film having the above structure, it increases cost and
thus is not practical. In addition, as for a method for producing
all of a laminated film of the tin oxide-based transparent
conductive film and the zinc oxide-based transparent conductive
film, by the sputtering method, because of reasons that the tin
oxide-based transparent conductive film with high transparency
cannot be produced by the sputtering method and the like, it is
said not attainable.
[0016] On the other hand, a method for obtaining the transparent
conductive film having zinc oxide as a major component, surface
irregularity and high haze ratio, by the sputtering method, has
been proposed (NON-PATENT LITERATURE 2). In this method, sputtering
film formation is performed using a sintered body target of zinc
oxide added with 2% by weight of Al.sub.2O.sub.3, under high gas
pressure of 3 to 12 Pa, at a substrate temperature of 200 to
400.degree. C. However, film formation is performed by charging
power of DC 80 W to a target with a size of 6 inch .PHI., therefore
input power density to the target is as extremely slow as 0.442
W/cm.sup.2. Therefore, film formation speed is as extremely low as
14 to 35 nm/min, and thus it is not practicable industrially.
[0017] In addition, a method for producing the transparent
conductive film with high haze ratio by obtaining the transparent
conductive film having zinc oxide as a major component, and small
surface irregularity, prepared by a conventional sputtering method,
and then by acid etching the surface of the film to make surface
roughening, has been proposed (NON-PATENT LITERATURE 3). However,
this method has problems of complicated process, high production
cost and the like, because after producing a film by the sputtering
method, which is a vacuum process, in a dry-type step, it requires
acid etching in atmosphere, drying and forming a semiconductor
layer by the CVD method of a dry-type step again.
[0018] As for AZO containing aluminum as a dopant, among materials
of the zinc oxide-based transparent conductive film, there has been
proposed a method for producing an AZO transparent conductive film
with orientation to a C axis, by a direct current magnetron
sputtering method, using a target having zinc oxide as a major
component and mixed with aluminum oxide (refer to PATENT LITERATURE
1). In this case, when film formation is performed by direct
current sputtering, under increased power density to be input to
the target, to perform film formation in high speed, generation of
arcing (abnormal discharge) happens frequently. Generation of
arcing in a production step of a film formation line may generate
film defect, or may not provide a film with predetermined
thickness, and thus makes impossible stable production of a high
quality transparent conductive film.
[0019] To overcome this problem, the present applicants have
proposed a sputter target with reduced abnormal discharge by using
zinc oxide as a major component mixed with gallium oxide, as well
as adding a third element (Ti, Ge, Al, Mg, In, Sn) (refer to PATENT
LITERATURE 2). Here, a GZO sintered body containing gallium as a
dopant has a ZnO phase, as a major constituent phase of the
structure, in which Ga and 2% by weight of at least one kind
selected from the group consisting of Ti, Ge, Al, Mg, In and Sn are
made as a solid solution, and other constituent phases are a ZnO
phase without a solid solution with at least one kind of the above
elements, or an intermediate compound phase represented by
ZnGa.sub.2O.sub.4 (spinel phase). In such a GZO target added with
the third element such as Al, although abnormal discharge as
described in PATENT LITERATURE 1 can be reduced, it was impossible
to completely eliminate it. In a continuous line of film formation,
even once generation of abnormal discharge results in a defect
product at that film formation time and influences production
yield.
[0020] To solve these problems, the present applicants have
proposed an oxide sintered body for a target, which hardly
generates particles even in performing continuous film formation
for a long period of time using a sputtering apparatus, and never
generates abnormal discharge even under inputting of high direct
current power, by optimization of content of aluminum and gallium
in the oxide sintered body having zinc oxide as a major component
and still more containing aluminum and gallium as addition
elements, as well as by optimum control of kind and composition of
crystalline phases, in particular, composition of the spinel phase
generating during firing (refer to PATENT LITERATURE 3).
[0021] Using this, the higher quality transparent conductive film
with lower resistance and higher transmittance as compared with
conventional ones can be formed, therefore it is applicable to
produce a solar cell with high conversion efficiency. However, in
recent years, a solar cell with further higher conversion
efficiency has been required, and high quality transparent
conductive film which can be used for such a purpose has been
required.
PRIOR ART DOCUMENTS
Patent Literatures
[0022] PATENT LITERATURE 1: 62-122011 [0023] PATENT LITERATURE 2:
10-306367 [0024] PATENT LITERATURE 3: 2008-110911
Non-Patent Literatures
[0024] [0025] NON-PATENT LITERATURE 1: K. Sato et al., "Hydrogen
Plasma Treatment of ZnO-Coated TCO Films", Proc. of 23th IEEE
Photovoltaic Specialists Conference, Louisville, 1993, pp. 855-859.
[0026] NON-PATENT LITERATURE 2: T. Minami, et. al., "Large-Area
Milkey Transparent Conducting Al-Doped ZnO Films Prepared by
Magnetron Sputtering", Japanese Journal of Applied Physics, [31]
(1992), pp. L1106-1109. [0027] NON-PATENT LITERATURE 3: J. Muller,
et. al., Thin Solid Films, 392 (2001), p. 327.
SUMMARY OF THE INVENTION
[0028] In view of the above circumstance, it is an object of the
present invention to provide a transparent conductive film, useful
in producing a highly efficient silicon-based thin film solar cell,
superior in hydrogen reduction resistance and superior in optical
confinement effect, a transparent conductive film laminated body
using the same, a production method therefor, and a silicon-based
thin film solar cell using this transparent conductive film or the
transparent conductive film laminated body, as an electrode.
[0029] The present inventors have intensively studied various
transparent conductive film materials as the transparent conductive
film to be used as a surface transparent electrode of a thin film
solar cell, to solve such conventional technical problems, and have
discovered that the zinc oxide-based transparent conductive film
containing zinc oxide as a major component and at least one or more
kinds of added metal elements selected from aluminum and gallium,
in which content of aluminum [Al] and content of gallium [Ga] are
within a specific range, and having a surface roughness (Ra) of
equal to or larger than 35.0 nm, and a surface resistance of equal
to or lower than 65 .OMEGA./.quadrature. is superior in hydrogen
reduction resistance and also superior in optical confinement
effect. In addition, we have discovered that by forming this zinc
oxide-based transparent conductive film on an indium oxide-based
transparent conductive film, the transparent conductive film can be
produced in high speed by the sputtering method only, and that the
transparent conductive film having superior hydrogen reduction
resistance, surface irregularity, high haze ratio, as well as high
conductivity can be obtained, and have thus completed the present
invention.
[0030] That is, according to a first aspect of the present
invention, there is provided a transparent conductive film
characterized by containing zinc oxide as a major component and at
least one or more kinds of added metal elements selected from
aluminum or gallium, whose content being within a range shown by
the following expression (1), and having a surface roughness (Ra)
of equal to or larger than 35.0 nm, and a surface resistance of
equal to or lower than 65 .OMEGA./.quadrature.
(wherein [Al] represents aluminum content expressed as atomicity
ratio (%) of Al/(Zn+Al); while [Ga] represents gallium content
expressed as atomicity ratio (%) of Ga/(Zn+Ga)).
[0031] In addition, according to a second aspect of the present
invention, there is provided the transparent conductive film in the
first aspect, characterized in that haze ratio is equal to or
higher than 8%.
[0032] In addition, according to a third aspect of the present
invention, there is provided the transparent conductive film in the
first aspect, characterized in that haze ratio is equal to or
higher than 10%.
[0033] In addition, according to a fourth aspect of the present
invention, there is provided the transparent conductive film in the
first aspect, characterized in that haze ratio is equal to or
higher than 16%.
[0034] In addition, according to a fifth aspect of the present
invention, there is provided the transparent conductive film in any
one of the first to the fourth aspects, characterized in that the
surface resistance is equal to or lower than 20
.OMEGA./.quadrature..
[0035] Still more, according to a sixth aspect of the present
invention, there is provided the transparent conductive film in the
fifth aspect, characterized in that the surface resistance is equal
to or lower than 15 .OMEGA./.quadrature..
[0036] On the other hand, according to a seventh aspect of the
present invention, there is provided a method for producing the
transparent conductive film in any one of the first to the sixth
aspects, for forming a zinc oxide-based transparent conductive film
(II) on a substrate, by a sputtering method, using an oxide
sintered body target containing zinc oxide as a major component and
at least one or more kinds of added metal elements selected from
aluminum and gallium, characterized by performing film formation in
high speed, by setting a direct current input power density of
equal to or higher than 1.66 W/cm.sup.2 to the aforesaid oxide
sintered body target, under condition of a sputtering gas pressure
of 2.0 to 15.0 Pa, and a substrate temperature of 200 to
500.degree. C.
[0037] In addition, according to an eighth aspect of the present
invention, there is provided a transparent conductive film
laminated body, characterized in that the zinc oxide-based
transparent conductive film (II) in any one of the first to the
sixth aspects was formed on an indium oxide-based transparent
conductive film (I) formed on the substrate.
[0038] Still more, according to a ninth aspect of the present
invention, there is provided the transparent conductive film
laminated body in the eighth aspect, characterized in that the
transparent conductive film (II) is a crystalline film comprising a
hexagonal crystalline phase.
[0039] In addition, according to a tenth aspect of the present
invention, there is provided the transparent conductive film
laminated body in the ninth aspect, characterized in that the
hexagonal crystalline phase has approximately c-axis orientation,
and a c-axis inclination angle is equal to or smaller than 10
degree, relative to a vertical direction of a substrate
surface.
[0040] In addition, according to an eleventh aspect of the present
invention, there is provided the transparent conductive film
laminated body in the eighth aspect, characterized in that the
indium oxide-based transparent conductive film (I) is a crystalline
film containing indium oxide as a major component and at least one
or more kinds of metal elements selected from Sn, Ti, W, Mo, and
Zr.
[0041] In addition, according to a twelfth aspect of the present
invention, there is provided the transparent conductive film
laminated body in the eighth or eleventh aspect, characterized in
that the indium oxide-based transparent conductive film (I)
comprises indium oxide as a major component and Sn, whose content
ratio is equal to or lower than 15% by atom, as atomicity ratio of
Sn/(In+Sn).
[0042] In addition, according to a thirteenth aspect of the present
invention, there is provided the transparent conductive film
laminated body in the eighth or eleventh aspect, characterized in
that the indium oxide-based transparent conductive film (I)
contains indium oxide as a major component and Ti, whose content
ratio is equal to or lower than 5.5% by atom, as atomicity ratio of
Ti/(In+Ti).
[0043] In addition, according to a fourteenth aspect of the present
invention, there is provided the transparent conductive film
laminated body in the eighth or eleventh aspect, characterized in
that the indium oxide-based transparent conductive film (I)
contains indium oxide as a major component and W, whose content
ratio is equal to or lower than 4.3% by atom, as atomicity ratio of
W/(In+W).
[0044] In addition, according to an fifteenth aspect of the present
invention, there is provided the transparent conductive film
laminated body in the eighth or eleventh aspect, characterized in
that the indium oxide-based transparent conductive film (I)
contains indium oxide as a major component and Zr, whose content
ratio is equal to or lower than 6.5% by atom, as atomicity ratio of
Zr/(In+Zr).
[0045] In addition, according to a sixteenth aspect of the present
invention, there is provided the transparent conductive film
laminated body in the eighth or eleventh aspect, characterized in
that the indium oxide-based transparent conductive film (I)
contains indium oxide as a major component and Mo, whose content
ratio is equal to or lower than 6.7% by atom, as atomicity ratio of
Mo/(In+Mo).
[0046] In addition, according to a seventeenth aspect of the
present invention, there is provided the transparent conductive
film laminated body in any one of the eighth to sixteenth aspects,
characterized in that the surface resistance is equal to or lower
than 20 .OMEGA./.quadrature..
[0047] Still more, according to an eighteenth aspect of the present
invention, there is provided the transparent conductive film
laminated body in any one of the eighth to seventeenth aspects,
characterized in that the haze ratio is equal to or higher than
12%.
[0048] On the other hand, according to a nineteenth aspect of the
present invention, there is provided a method for producing the
transparent conductive film laminated body in any one of the eighth
to eighteenth aspects, characterized by firstly forming a
crystalline film of the indium oxide-based transparent conductive
film (I) on a substrate, by a sputtering method, using an oxide
sintered body target comprising indium oxide as a major component
containing at least one or more kinds of metal elements selected
from Sn, Ti, W, Mo, and Zr, and then forming the zinc oxide-based
transparent conductive film (II) on the indium oxide-based
transparent conductive film (I), by switching to an oxide sintered
body target containing zinc oxide as a major component and at least
one or more kinds of added metal elements selected from aluminum
and gallium.
[0049] In addition, according to a twentieth aspect of the present
invention, there is provided the method for producing the
transparent conductive film laminated body in the nineteenth
aspect, characterized in that the indium oxide-based transparent
conductive film (I) is formed as an amorphous film, under condition
of a substrate temperature of equal to or lower than 100.degree. C.
and a sputtering gas pressure of 0.1 to 1.0 Pa, and subsequently
crystallized by heat treatment at 200 to 400.degree. C.
[0050] Still more, according to a twenty-first aspect of the
present invention, there is provided the method for producing the
transparent conductive film laminated body in nineteenth aspect,
characterized in that the indium oxide-based transparent conductive
film (I) is formed as a crystalline film, under condition of a
substrate temperature of 200 to 400.degree. C. and a sputtering gas
pressure of 0.1 to 1.0 Pa.
[0051] On the other hand, according to a twenty-second aspect of
the present invention, there is provided a silicon-based thin film
solar cell, wherein the transparent conductive film in any one of
the first to the sixth aspects, or the transparent conductive film
laminated body in any one of the eighth to the seventeenth aspects
is formed on a translucent substrate, at least one kind of a unit
selected from one conducting type semiconductor layer unit, a
photoelectric conversion layer unit, and other conducting type
semiconductor layer unit, is arranged on said transparent
conductive film or said transparent conductive film laminated body,
and a back surface electrode layer is arranged on said unit.
[0052] According to the present invention, the transparent
conductive film superior in hydrogen reduction resistance, surface
irregularity, high haze ratio, as well as high conductivity can be
provided, because of containing zinc oxide as a major component and
at least one or more kinds of added metal elements selected from
aluminum and gallium, in a specific amount, and having a surface
roughness (Ra) of equal to or larger than 35.0 nm, and a surface
resistance of equal to or lower than 65 .OMEGA./.quadrature..
[0053] Still more, because this transparent conductive film can be
produced by only the sputtering method, it is superior as a surface
transparent electrode of the thin film solar cell, and is
industrially useful. In addition, the surface transparent electrode
of the thin film solar cell with lower resistance can be obtained
by laminating the above transparent conductive film on other
transparent conductive film having lower resistance to make a
transparent conductive film laminated body, and said transparent
conductive film laminated body can be provided in lower price as
compared with the transparent conductive film by a conventional
thermal CVD method. Therefore, it is industrially extremely useful,
because a silicon-based thin film solar cell with high efficiency
can be provided by a simple process and in low price.
BRIEF DESCRIPTION OF THE DRAWINGS
[0054] FIG. 1 is an illustrative drawing showing a schematic
composition of a silicon-based thin film solar cell of the present
invention, using an amorphous silicon thin film as a photoelectric
conversion unit.
[0055] FIG. 2 is an illustrative drawing showing a schematic
composition of a silicon-based hybrid thin film solar cell of the
present invention, in which an amorphous silicon thin film and a
crystalline silicon thin film are laminated as a photoelectric
conversion unit.
[0056] FIG. 3 is a graph showing relation of contents of aluminum
and gallium, in a transparent conductive film of the present
invention.
[0057] FIG. 4 is a surface SEM photo of a transparent conductive
thin film obtained by a production method of the present
invention.
NOTATION
[0058] 1 Translucent substrate [0059] 2 Surface transparent
electrode layer [0060] 3 Amorphous photoelectric conversion unit
[0061] 4 Crystalline photoelectric conversion unit [0062] 5 Back
surface electrode
DETAILED DESCRIPTION OF THE INVENTION
[0063] Explanation will be given below in detail on the transparent
conductive film, the transparent conductive film laminated body and
the production method therefor, and the silicon-based thin film
solar cell, with reference to drawings.
1. The Zinc Oxide-Based Transparent Conductive Film
[0064] The transparent conductive film of the present invention is
characterized by containing zinc oxide as a major component and at
least one or more kinds of added metal elements selected from
aluminum and gallium, whose content being within a range shown by
the following expression (1), and having a surface roughness (Ra)
of equal to or larger than 35.0 nm, and a surface resistance of
equal to or lower than 65 .OMEGA./.quadrature.
--[Al]+0.30.ltoreq.[Ga].ltoreq.-2.68.times.[Al]+1.74 (1)
(wherein [Al] represents aluminum content expressed as atomicity
ratio (%) of Al/(Zn+Al); while [Ga] represents gallium content
expressed as atomicity ratio (%) of Ga/(Zn+Ga)).
[0065] In the transparent conductive film of the present invention,
a content of aluminum [Al] and a content of gallium [Ga] should be
in relation shown by the expression (1), and composition thereof
should be within a range of an oblique line part of FIG. 3.
[0066] The content of aluminum and gallium in the transparent
conductive film of more than the range specified by the expression
(1) provides easy diffusion of aluminum and gallium in the
silicon-based thin film formed on said transparent conductive film,
and generates a problem of not attainable the silicon-based thin
film solar cell with superior characteristics. In addition, in view
of productivity, the content of aluminum and gallium in said
transparent conductive film of more than the range specified by the
expression (1) results in making impossible to produce the
transparent conductive film with large surface irregularity and
high haze ratio in high speed by a sputtering method. On the other
hand, the content of less than the range specified by the
expression (1) results in insufficient conductivity, which makes
impossible utilization as a surface transparent electrode of the
solar cell.
[0067] The surface roughness (Ra) of the transparent conductive
film of the present invention is equal to or larger than 35.0 nm.
The surface roughness (Ra) below 35.0 nm cannot provide the zinc
oxide-based transparent conductive film with high haze ratio, and
provides inferior optical confinement effect when the silicon-based
thin film solar cell is produced, and cannot attain high conversion
efficiency. To provide sufficient optical confinement effect, Ra is
preferably equal to or larger than 35.0 nm, and as large as
possible. However, the surface roughness (Ra) of said transparent
conductive film over 70 nm affects growth of a silicon-based thin
film to be formed on said transparent conductive film, deteriorates
contact between said transparent conductive film and the
silicon-based thin film caused by generation of a gap at the
interface, deteriorates characteristics of the solar cell, and thus
is not preferable.
[0068] According to NON-PATENT LITERATURE 2, a film with increased
addition amount of Al and surface irregularity cannot be formed
unless in low speed. Film formation in high speed results in
decrease in the surface irregularity. Desired shape of the surface
irregularity also cannot be obtained by film formation in high
speed. Decreased addition amount of Al in the transparent
conductive film has not been investigated at all up to now, because
it leads to increase in resistance value, and the surface
irregularity or shape thereof of the film had not been investigate
as well, in the case of increasing film formation speed. The
surface irregularity of the transparent conductive film of the
present invention is largely different from shape obtained in a
range of NON-PATENT LITERATURE 2.
[0069] In addition, the surface resistance of the transparent
conductive film of the present invention should be equal to or
lower than 65 .OMEGA./.quadrature.. The surface resistance over 65
.OMEGA./.quadrature. increases power loss at the surface electrode,
in utilization as the surface electrode of the solar cell, and
cannot attain the solar cell with high efficiency. The transparent
conductive film of the present invention can have the surface
resistance of equal to or lower than 65 .OMEGA./.quadrature. by
taking such a film composition as described above. The surface
resistance of the zinc oxide-based transparent conductive film of
the present invention is preferably equal to or lower than 20
.OMEGA./.quadrature., and still more preferably equal to or lower
than 15 .OMEGA./.quadrature..
[0070] The zinc oxide-based transparent conductive film used as the
surface electrode can attain the solar cell with high efficiency,
even by large cell area, because the lower surface resistance
provides the smaller power loss at the surface electrode part, and
thus is preferable. This can be attained by making the zinc
oxide-based transparent conductive film a crystalline film. On the
contrary, the high surface resistance of the surface electrode
increases power loss at the surface electrode to an unignorable
level, in the case of large cell size of the solar cell, which thus
requires decrease in cell area and wiring of many small-type cells
with metal wiring having low resistance so as to increase the area.
The surface electrode having the surface resistance of equal to or
lower than 65 .OMEGA./.quadrature. can attain the solar cell with
at least 5 cm.quadrature.; the surface resistance of equal to or
lower than 20 .OMEGA./.quadrature. can attain the solar cell with
at least 8 cm.quadrature.; and still more the surface resistance of
equal to or lower than 15 .OMEGA./.quadrature. can attain the solar
cell with at least 12 cm.quadrature., without considering influence
of power loss at the surface electrode.
[0071] The solar cell with small cell area requires connection with
metal wiring, which has a problem of not only lowering of
generation amount per unit area of one module prepared by cell
connection, caused by an increased cell gap, but also increasing
production cost per unit cell area, and thus is not preferable.
[0072] The haze ratio of the zinc oxide-based transparent
conductive film of the present invention is preferably set at equal
to or higher than 8%. As described above, because the zinc
oxide-based transparent conductive film of the present invention
has the surface roughness (Ra) of equal to or larger than 35.0 nm,
the haze ratio of equal to or higher than 8% can also be attained.
The haze ratio is preferably equal to or higher than 10%, and more
preferably equal to or higher than 16%. The higher haze ratio
provides the more superior optical confinement effect, and thus can
attain a solar cell with the higher efficiency. This can be
attained by film formation of the zinc oxide-based transparent
conductive film under sputtering condition to be described later.
In comparing with a solar cell having the same structure, position
showing increased conversion efficiency caused by optical
confinement effect, relative to a surface electrode with the haze
ratio of approximately 0%, is in the surface electrode with the
haze ratio of equal to or higher than 8%. In a standard
silicon-based thin film solar cell having a single structure, in
order to attain the conversion efficiency of equal to or higher
than 8%, the haze ratio of equal to or higher than 10% is
essential. In addition, in similar evaluation, in order to attain
the conversion efficiency of equal to or higher than 12%, use of a
surface electrode with the haze ratio of equal to or higher than
16% is effective.
[0073] The zinc oxide-based transparent conductive film of the
present invention is superior in hydrogen reduction resistance, has
surface irregularity, high haze ratio, and high conductivity, as
well as can be produced by only the sputtering method, therefore it
is superior as the transparent conductive film for the surface
transparent electrode of the thin film solar cell.
2. A Production Method for the Zinc-Oxide Based Transparent
Conductive Film
[0074] A method for producing the zinc-oxide based transparent
conductive film of the present invention is a method for producing
the transparent conductive film for forming the zinc-oxide based
transparent conductive film (II) on a substrate, by a sputtering
method, using an oxide sintered body target containing zinc oxide
as a major component and at least one or more kinds of added metal
elements selected from aluminum and gallium, characterized by
performing film formation in high speed, by setting a direct
current input power density of equal to or higher than 1.66
W/cm.sup.2 to the aforesaid oxide sintered body target, under
condition of a sputtering gas pressure of 2.0 to 15.0 Pa, and a
substrate temperature of 200 to 500.degree. C.
[0075] In the present invention, as a target, the oxide sintered
body containing zinc, aluminum and gallium is used, in which the
content of aluminum and gallium is within a range shown by the
following expression (1):
--[Al]+0.30.ltoreq.[Ga].ltoreq.-2.68.times.[Al]+1.74 (1)
(wherein [Al] represents aluminum content expressed as atomicity
ratio (%) of Al/(Zn+Al); while [Ga] represents gallium content
expressed as atomicity ratio (%) of Ga/(Zn+Ga)).
[0076] When the content of aluminum and gallium is within the range
specified by the expression (1), the zinc oxide-based transparent
conductive film of the present invention having large surface
irregularity and high haze ratio as above can be produced in high
speed by the sputtering method.
[0077] It should be noted that, when the content of aluminum and
gallium is more than the range specified by the expression (1) (the
upper right range from the oblique line part region of FIG. 3), a
film having large surface irregularity cannot be obtained by the
sputtering method in high speed, while when the content of aluminum
and gallium is less than the range specified by the expression (1)
(the lower left range from the oblique line part region of FIG. 3),
only a film with insufficient conductivity is obtained, and thus in
any of these cases, the film cannot be utilized as the surface
transparent electrode of the solar cell.
[0078] The increased addition amount of a material with high
melting point such as aluminum oxide or gallium oxide to zinc oxide
retards crystal growth of the film in film formation, therefore
input power to the target is increased to increase supply amount of
sputtering particles onto the substrate, which in turn inhibits
increase in irregularity caused by crystal growth. Such a
composition of aluminum and gallium as above is capable of
providing a film with large crystal grains of the film and large
surface irregularity, even in high speed film formation by a high
input power of equal to or higher than 1.66 W/cm.sup.2.
[0079] This oxide sintered body can be produced by adding and
mixing gallium oxide powder and aluminum oxide powder to zinc oxide
powder, as raw material powder, then subsequently pulverizing and
mixing treating the resultant slurry obtained by blending an
aqueous medium to this raw material powder, then molding the
resultant mixture, and after that firing the molded body.
Description on the detailed production method has been given in the
above PATENT LITERATURE 3.
[0080] It should be noted that, in this oxide sintered body, other
than zinc or aluminum or gallium or oxygen, other elements (for
example, indium, titanium, tungsten, molybdenum, iridium,
ruthenium, rhenium, cerium, magnesium, silicon, fluorine and the
like) may be contained within a range not to impair objects of the
present invention.
[0081] In the present invention, the zinc oxide-based transparent
conductive film having large surface irregularity and high haze
ratio can be produced in high speed, by setting a sputtering gas
pressure at 2.0 to 15.0 Pa, and a substrate temperature at 200 to
500.degree. C. Film formation in high speed means to perform
sputtering film formation by increasing input power to the target
to equal to or higher than 1.66 W/cm.sup.2. In this way, the zinc
oxide-based transparent conductive film having large surface
irregularity and high haze ratio can be produced, for example, even
in high speed film formation at equal to or higher than 40 nm/min,
in static opposing film formation. It should be noted that, use of
such a target as also used in NON-ATENT LITERATURE 2, having a
target composition over 3% by atom as Al/(Zn+Al), can provide only
a film with poor surface irregularity and small haze ratio, when
film formation is performed in high speed by increasing input
power. In addition, also even in the use of a target, having a
target composition over 2% by atom as Ga/(Zn+Ga), can provide only
a film with poor surface irregularity and small haze ratio, when
film formation is performed in high speed by increasing input
power.
[0082] It should be noted that, the present invention can also be
applied to transfer film formation (passage-type film formation).
In the passage-type film formation, in which film formation is
performed by making the substrate passing on the target, the zinc
oxide-based transparent conductive film with superior surface
irregularity and high haze ratio can be obtained, even in high
speed transfer film formation of 3.5 nmm/min, (resulting film
thickness (nm) is calculated by dividing with carry rate (m/min)),
for example, in which the film is formed under the similar input
power density. It should be noted that, film formation speed in
this case is not especially limited as long as object of the
present invention can be attained.
[0083] In addition, the present invention can be applied to
planer-type magnetron-system sputtering film formation using a
plate-like target, and also to rotary-type magnetron-system
sputtering film formation using a cylinder-shape target.
[0084] The sputtering gas pressure below 2.0 Pa makes difficult to
obtain a film with large surface irregularity, and makes impossible
to obtain a film with a Ra value of equal to or larger than 35.0
nm. On the other hand, the sputtering gas pressure over 15.0 Pa
results in delaying film formation speed, and thus is not
preferable. For example, in order to obtain a high film formation
speed of equal to or higher than 40 nm/min, by inputting high power
with a direct current input power density to the target of equal to
or higher than 1.66 W/cm.sup.2, in static opposing film formation,
the sputtering gas pressure should be equal to or lower than 15.0
Pa.
[0085] Conductivity of the zinc oxide-based transparent conductive
film largely depends on substrate heating temperature in film
formation. It is because high temperature in substrate heating
provides good crystallinity of the film and increases mobility of
carrier electrons. In the present invention, it is preferable that
the substrate is heated at 200 to 500.degree. C., and in
particular, 300 to 500.degree. C. Film formation under heating the
substrate at high temperature provides good crystallinity of the
resultant transparent conductive film and can attain superior
conductivity caused by the above factor.
3. The Transparent Conductive Film Laminated Body
[0086] The transparent conductive film of the present invention can
be used as a transparent conductive film laminated body for the
surface electrode of the thin film solar cell with lower
resistance. In the transparent conductive film laminated body of
the present invention, the above zinc oxide-based transparent
conductive film (II) is formed on the surface of the indium
oxide-based transparent conductive film (I) formed on the
translucent substrate.
[0087] In the transparent conductive film laminated body of the
present invention, the zinc oxide-based transparent conductive film
(II) contains zinc oxide as a major component and at least one or
more kinds of added metal elements selected from aluminum and
gallium, whose content being within a range shown by the following
expression (1):
--[Al]+0.30.ltoreq.[Ga].ltoreq.-2.68.times.[Al]+1.74 (1)
(wherein [Al] represents aluminum content expressed as atomicity
ratio (%) of Al/(Zn+Al); while [Ga] represents gallium content
expressed as atomicity ratio (%) of Ga/(Zn+Ga)).
[0088] The content of aluminum and gallium in the zinc oxide-based
transparent conductive film of more than the range specified by the
expression (1) provides easy diffusion of aluminum and gallium in
the silicon-based thin film formed thereon, and cannot attain the
silicon-based thin film solar cell with superior characteristics.
In addition, in view of productivity, the content of aluminum and
gallium in the film of more than the range specified by the
expression (1) results in making impossible to produce the
transparent conductive film with large surface irregularity and
high haze ratio in high speed by a sputtering method. On the other
hand, the content of less than the range specified by the
expression (1) results in insufficient conductivity, which makes
impossible utilization as a surface transparent electrode of the
solar cell.
[0089] Surface roughness (Ra) of zinc oxide-based transparent
conductive film of the present invention is preferably equal to or
larger than 35.0 nm. The surface roughness (Ra) below 35.0 nm
cannot provide zinc oxide-based transparent conductive film with
high haze ratio, and thus provides inferior optical confinement
effect and cannot attain high conversion efficiency, in preparation
of a silicon-based thin film solar cell. In order to maintain
sufficient optical confinement effect, the surface roughness (Ra)
is preferably equal to or larger than 35.0 nm, and as large as
possible.
[0090] However, the surface roughness (Ra) of said transparent
conductive film over 70 nm affects growth of the silicon-based thin
film formed on said transparent conductive film, generates space at
the interface between said transparent conductive film and the
silicon-based thin film, and thus deteriorates contact between
them, and deteriorates solar cell characteristics, and thus is not
preferable.
[0091] Surface resistance of the transparent conductive film
laminated body of the present invention is equal to or lower than
65 .OMEGA./.quadrature.. The surface resistance over 65
.OMEGA./.quadrature. increases power loss at the surface electrode,
in applying to the surface electrode of the solar cell, and thus
cannot attain the solar cell with high efficiency. The transparent
conductive film laminated body of the present invention can take
surface resistance of equal to or lower than 65
.OMEGA./.quadrature. because of having such a laminated structure
as above.
[0092] Surface resistance of the transparent conductive film
laminated body of the present invention is preferably equal to or
lower than 20 .OMEGA./.quadrature., more preferably equal to or
lower than 13 .OMEGA./.quadrature., still more preferably equal to
or lower than 10 .OMEGA./.quadrature., and most preferably equal to
or lower than 8 .OMEGA./.quadrature.. Reason for attainable such
surface resistance is that such a structure is adopted as the
indium oxide-based transparent conductive film with the above
characteristics is inserted to a base.
[0093] As described above, the zinc oxide-based transparent
conductive film used as the surface electrode can attain the solar
cell with high efficiency, even it has large cell area, because the
lower surface resistance provides the smaller power loss at the
surface electrode part, and thus is preferable. On the contrary,
the high surface resistance of the surface electrode increases
power loss at the surface electrode to an unignorable level, in the
case of large cell size of the solar cell, which thus requires
decrease in cell area and wiring of many small-size cells with
metal wiring having low resistance so as to increase the area. The
surface electrode having the surface resistance of equal to or
lower than 65 .OMEGA./.quadrature. can attain the solar cell with
at least 5 cm.quadrature., but the surface resistance of equal to
or lower than 20 .OMEGA./.quadrature. can attain the solar cell
with at least 8 cm.quadrature.; and still more the surface
resistance of equal to or lower than 13 .OMEGA./.quadrature. can
attain the solar cell with at least 15 cm.quadrature., the surface
resistance of equal to or lower than 10 .OMEGA./.quadrature. can
attain the solar cell with at least 17 cm.quadrature., and the
surface resistance of equal to or lower than 8 .OMEGA./.quadrature.
can attain the solar cell with at least 20 cm.quadrature., without
considering influence of power loss at the surface electrode. The
solar cell with small cell area requires connection with metal
wiring, which has a problem of not only lowering of generation
amount per unit area of one module prepared by cell connection,
caused by an increased cell gap, but also increasing production
cost per unit cell area, and thus is not preferable.
[0094] In addition, the haze ratio of the transparent conductive
film laminated body of the present invention is more preferably
equal to or higher than 12%, still more preferably equal to or
higher than 16%, and most preferably equal to or higher than 20%,
and thus provides very high optical confinement effect. Reason for
attaining such high haze ratio is that the indium oxide-based
transparent conductive film with the above characteristics is
inserted to a base. In a standard silicon-based thin film solar
cell having a single structure, in order to attain the conversion
efficiency of equal to or higher than 10%, the haze ratio of equal
to or higher than 12% is essential. In addition, in similar
evaluation, in order to attain the conversion efficiency of equal
to or higher than 12%, use of a surface electrode with the haze
ratio of equal to or higher than 16% is effective. Still more, in
similar evaluation, in order to attain the conversion efficiency of
equal to or higher than 15%, use of a surface electrode with the
haze ratio of equal to or higher than 20% is effective. In the
tandem-type silicon-based thin film solar cell with high
efficiency, a surface electrode with the haze ratio of equal to or
higher than 20% is particularly useful.
[0095] In addition, it is preferable that the zinc oxide-based
transparent conductive film (II) in the transparent conductive film
laminated body of the present invention is a crystalline film
containing a hexagonal crystalline phase and has superior
approximately c-axis orientation, with a c-axis inclination angle
being equal to or smaller than 15 degree, in particular, equal to
or smaller than 10 degree, relative to a vertical direction of a
substrate.
[0096] In this way, the transparent conductive film laminated body
with large surface roughness, high haze ratio as above and low
resistance can be attained. In evaluation of orientation of a
ZnO-based sputtering film with a conventional thin film X-ray
diffraction measurement (.theta.-2.theta.), only a diffraction peak
caused by c-axis orientation was measured and it has been judged
that most parts belonged to c-axis orientation. It is because, in
the conventional thin film XRD measurement, only diffraction caused
by plane spacing of lattice planes (for example, (002) plane or
(004) plane) of the c-axis direction was observed, even when the
c-axis was inclined a little from a vertical direction of the
substrate. However, the present applicants have clarified, from
pursuit by measurement of an X-ray pole figure, that the c-axis of
the film does not necessarily grow in the vertical direction of the
substrate surface, but a little inclined relative to the vertical
direction. In the case of the transparent conductive film laminated
body such as in the present invention, high haze ratio can be
attained, when it has superior approximate c-axis orientation, that
is, inclination angle of the c-axis of the zinc oxide-based
transparent conductive film (II) relative to the vertical direction
of the substrate surface is equal to or smaller than 10 degree.
And, still more, degree of the inclination of the c-axis of the
zinc oxide-based transparent conductive film (II) of the
transparent conductive film laminated body such as the present
invention depends largely on production condition of the indium
oxide-based transparent conductive film (I) of the base.
[0097] In order to obtain the transparent conductive film laminated
body with lower resistance from the transparent conductive film
laminated body of the present invention, the indium oxide-based
transparent conductive film (I) should be used as the base of the
zinc oxide-based transparent conductive film (II). That is, said
indium oxide-based transparent conductive film (I) is a crystalline
film containing indium oxide as a major component and at least one
or more kinds of metal elements selected from Sn, Ti, W, Mo, and
Zr. The crystalline film of indium oxide containing the addition
element of Sn, Ti, W, Mo, or Zr is superior in conductivity, and
thus is useful. In particular, containment of the element of Ti, W,
Mo, or Zr can provide a film with high mobility. Therefore, low
resistance is attained without increasing carrier concentration,
and thus a film with low resistance and high transmittance from a
visible region to a near infrared region can be attained.
[0098] In the case of containing indium oxide as a major component
and Sn, the content ratio thereof is preferably equal to or lower
than 15% by atom, as atomicity ratio of Sn/(In+Sn), in the case of
containing Ti, the content ratio thereof is preferably equal to or
lower than 5.5% by atom, as atomicity ratio of Ti/(In+Ti), in the
case of containing W, the content ratio thereof is preferably equal
to or lower than 4.3% by atom, as atomicity ratio of W/(In+W), in
the case of containing Zr, the content ratio thereof is preferably
equal to or lower than 6.5% by atom, as atomicity ratio of
Zr/(In+Zr), and in the case of containing Mo, the content ratio
thereof is preferably equal to or lower than 6.7% by atom, as
atomicity ratio of Mo/(In+Mo). Containment over this range provides
high resistance, and thus is not useful.
[0099] In order to obtain the transparent conductive film laminated
body of the present invention, it is desirable to adopt the
following condition in forming the indium oxide-based transparent
conductive film (I) of the base. That is, a crystalline film of the
indium oxide-based transparent conductive film (I) is formed on a
substrate, by a sputtering method, using an oxide sintered body
target containing indium oxide as a major component containing at
least one or more kinds of metal elements selected from Sn, Ti, W,
Mo, and Zr, and then the zinc oxide-based transparent conductive
film (II) is formed on the indium oxide-based transparent
conductive film (I), by switching to an oxide sintered body target
containing zinc oxide as a major component and at least one or more
kinds of added metal elements selected from aluminum and
gallium.
[0100] As a formation method for the indium oxide-based transparent
conductive film (I), there are the first method for forming an
amorphous film without heating a substrate, and then crystallizing
it by heat treatment, and the second method for forming a
crystalline film by heating the substrate.
[0101] In the first method, an amorphous film is formed, under
condition of a substrate temperature of equal to or lower than
100.degree. C. and a sputtering gas pressure of 0.1 to 1.0 Pa, and
subsequently it is crystallized by heat treatment at 200 to
400.degree. C. to obtain the indium oxide-based transparent
conductive film. In addition, in the second method, the indium
oxide-based transparent conductive film is formed as the
crystalline film under condition of a substrate temperature of 200
to 400.degree. C. and a sputtering gas pressure of 0.1 to 1.0
Pa.
[0102] In the present invention, as a formation method for the
indium oxide-based transparent conductive film (I), similarly as in
the zinc oxide-based transparent conductive film (II), planer-type
magnetron-system sputtering film formation using a plate-like
target can be applied, and also rotary-type magnetron-system
sputtering film formation using a cylinder-shape target can be
applied.
[0103] In the present invention, the first method, in which an
amorphous film is formed without heating the substrate, is better
than the second method, in which a crystalline film is formed by
heating the substrate. It is because the first method can provide a
film with larger surface roughness (Ra) and higher haze ratio.
[0104] The transparent conductive film laminated body obtained by
such a production method is useful as a surface electrode of a
highly efficient solar cell, due to having high haze ratio and low
resistance value.
[0105] In the present invention, thickness of the transparent
conductive film is not especially limited, and although it depends
on a material composition, the indium oxide-based transparent
conductive film (I) is 40 to 400 nm, and particularly preferably 45
to 300 nm, in addition, the zinc oxide-based transparent conductive
film (II) is 500 to 1700 nm, and particularly preferably 700 to
1620 nm. The above transparent conductive film of the present
invention has low resistance and high transmittance of solar ray
containing from visible light to near infrared light covering a
wavelength of 380 nm to 1200 nm, therefore it can extremely
efficiently convert light energy of solar ray to electric
energy.
4. The Thin Film Solar Cell
[0106] In the thin film solar cell of the present invention, the
above transparent conductive film, or the above transparent
conductive film laminated body is formed on a translucent
substrate, and at least one kind of a unit selected from one
conducting type semiconductor layer unit, a photoelectric
conversion layer unit, and other conducting type semiconductor
layer unit, is arranged on the aforesaid transparent conductive
film or transparent conductive film laminated body, and a back
surface electrode layer is arranged on said unit.
[0107] In general, a thin film solar cell contains a transparent
conductive film, one or more semiconductor thin film photoelectric
conversion units and a back surface electrode, laminated
sequentially on a translucent substrate. And, one photoelectric
conversion unit contains a p-type layer, an n-type layer and an
i-type layer sandwiched between them. A structure of this
representative silicon-based amorphous thin film solar cell is
shown in FIG. 1.
[0108] The p-type or n-type conductive-type semiconductor layer
fulfills a role of generating inner electric field inside the
photoelectric conversion unit, and value of open circuit voltage
(Voc), which is one of important characteristics of the thin film
solar cell, depends on intensity of this inner electric field. The
i-type layer is substantially an intrinsic semiconductor layer and
occupies a large portion of thickness of the photoelectric
conversion unit, and photoelectric conversion action generates
mainly inside this i-type layer. Therefore, this i-type layer is
usually called an i-type photoelectric conversion layer, or simply
a photoelectric conversion layer. The photoelectric conversion
layer is not limited to the intrinsic semiconductor layer, but may
be a layer doped in the p-type or the n-type in trace amount within
a range not to raise a loss problem of light absorbed by doped
impurities (dopants).
[0109] In the silicon-based thin film solar cell using a
silicon-based thin film as the photoelectric converting unit (a
light absorbing layer), other than amorphous thin film solar cells,
such one has also been practically used as a micro crystalline thin
film solar cell, or a crystalline thin film solar cell, as well as
a hybrid thin film solar cell obtained by laminating these. Here,
the photoelectric converting unit or the thin film solar cell, as
described above, in which the photoelectric converting layer
occupying a major part thereof is amorphous is called an amorphous
unit or an amorphous thin film solar cell, while one in which the
photoelectric converting layer is crystalline is called a
crystalline unit or a crystalline thin film solar cell, and one in
which the photoelectric converting layer is micro crystalline is
called a micro crystalline unit or a micro crystalline thin film
solar cell.
[0110] As a method for enhancing conversion efficiency of such a
thin film solar cell, there is a method for making a tandem-type
solar cell by laminating two or more photoelectric conversion
units. In this method, by arranging a front unit containing the
photoelectric conversion layer having a large band gap at a light
injection side of the thin film solar cell, and by arranging a rear
unit containing the photoelectric conversion layer having a small
band gap in order at the rear part thereof, photoelectric
conversion over a wide wavelength range of injected light is made
possible, and in this way, enhancement of conversion efficiency as
the whole solar cell is attained. In this tandem-type solar cell, a
representative structure of, in particular, a hybrid thin film
solar cell, in which an amorphous photoelectric conversion unit and
a crystalline or micro crystalline photoelectric conversion unit
are laminated, is shown in FIG. 2. In the hybrid thin film solar
cell, for example, wavelength of light, which the i-type amorphous
silicon can convert photoelectrically, is up to about 800 nm, in a
long wavelength side, however, the i-type crystalline or
microcrystalline silicon can convert photoelectrically light up to
about 1150 nm longer than that.
[0111] The transparent conductive film of the present invention can
be produced using only the sputtering method, and can provide a
transparent conductive film having high productivity, as well as
superior hydrogen reduction resistance, surface irregularity, high
haze ratio, and what is called superior optical confinement effect,
along with low resistance, and still more can provide a transparent
conductive film laminated body in which said transparent conductive
film is laminated on other transparent conductive film with low
resistance, that is, the indium oxide-based transparent conductive
film (I). In addition, it is capable of providing a silicon-based
thin film solar cell having said transparent conductive film or
transparent conductive film laminated body, as an electrode.
[0112] In addition, the silicon-based thin film solar cell of the
present invention has the above zinc oxide-based transparent
conductive film with large surface irregularity, high haze ratio
and low resistivity, or the above transparent conductive film
laminated body, and is arranged thereon with at least one kind of a
unit selected from one conducting type semiconductor layer unit, a
photoelectric conversion layer unit, or other conducting type
semiconductor layer unit, and is arranged thereon with a back
surface electrode layer.
[0113] Explanation will be given next in more specifically on
components of the silicon-based thin film solar cell of the present
invention. In FIGS. 1 and 2, on a translucent substrate 1, a zinc
oxide-based transparent conductive film 2 of the present invention
is formed. As the translucent substrate 1, a plate-like member or a
sheet-like member composed of glass, a transparent resin or the
like, is used. On the transparent conductive film 2, an amorphous
photoelectric conversion unit 3 is formed. The amorphous
photoelectric conversion unit 3 is composed of an amorphous p-type
silicon carbide layer 3p, a non-doped amorphous i-type silicon
photoelectric conversion layer 31 and an n-type silicon-based
interface layer 3n. The amorphous p-type silicon carbide layer 3p
is formed at a substrate temperature of equal to or lower than
180.degree. C. to prevent decrease in transmittance caused by
reduction of the transparent conductive film 2.
[0114] In FIG. 2, on the amorphous photoelectric conversion unit 3,
a crystalline photoelectric conversion unit 4 is formed. The
crystalline photoelectric conversion unit 4 is composed of a
crystalline p-type silicon layer 4p, a crystalline i-type silicon
photoelectric conversion layer 4i and a crystalline n-type silicon
layer 4n. For formation of the amorphous photoelectric conversion
unit 3 and the crystalline photoelectric conversion unit 4
(hereafter, both of these are collectively referred to simply as a
photoelectric conversion unit), a high frequency plasma CVD method
is suitable. As formation condition of the photoelectric conversion
unit, a substrate temperature of 100 to 250.degree. C. (however,
for the amorphous p-type silicon carbide layer 3p, it is equal to
or lower than 180.degree. C.), a pressure of 30 to 1500 Pa, and a
high frequency power density of 0.01 to 0.5 W/cm.sup.2 are
preferably used. As raw material gas used in forming the
photoelectric conversion unit, silicon-containing gas such as
SiH.sub.4, Si.sub.2H.sub.6, or a mixture of these gas and hydrogen
is used. As dopant gas for forming the p-type or the n-type layer
in the photoelectric conversion unit, B.sub.2H.sub.6 or PH.sub.3 or
the like is preferably used.
[0115] On the crystalline n-type silicon layer 4n of an interface
layer, a back surface electrode 5 is formed. The back surface
electrode 5 is composed of a back surface transparent electrode
layer 5t and a back surface reflective electrode layer 5m. As the
back surface transparent electrode layer 5t, a metal oxide obtained
by conventional technology, such as ZnO or ITO, is enough, and as
the back surface reflective electrode layer 5m, Ag, Al or an alloy
thereof is preferably used. In forming the back surface electrode
5, a method such as sputtering or vapor deposition is preferably
used. The back surface electrode 5 is usually set to have a
thickness of 0.5 to 5 .mu.m, and preferably 1 to 3 .mu.m. It should
be noted that, in FIG. 2, a structure of the hybrid thin film solar
cell is shown, however, the photoelectric conversion unit is not
necessarily present in two units, and it may be a single structure
of amorphous or crystalline substance, or a laminated-type solar
cell structure of three or more layers. After formation of the back
surface electrode 5, by heating it under the vicinity of
atmospheric pressure at an ambient temperature of equal to or
higher than formation temperature of the amorphous p-type silicon
carbide layer 3p, the silicone-based thin film solar cell of the
present invention is completed. As vapor to be used as heating
atmosphere, air, nitrogen, mixture of nitrogen and oxygen or the
like is used preferably. In addition, the vicinity of atmospheric
pressure shows a range of approximately 0.5 to 1.5 atm.
EXAMPLES
[0116] Explanation will be given below on the zinc oxide-based
transparent conductive film according to the present invention with
comparing Examples and Comparative Examples. It should be noted
that, the zinc oxide-based transparent conductive film of the
present invention should not be limited by these Examples.
(1) Film thickness was measured by the following procedure. Before
film formation, a permanent marker was applied in advance on a part
of a substrate, and after the film formation, the permanent marker
was wiped off with ethanol to form a part not formed with the film
and to determine by measuring the step difference between the parts
with and without the film, using a contact-type surface shape
measurement apparatus (Alpha-Step IQ, manufactured by KLA Tencor
Co., Ltd.). (2) In addition, composition of the resultant
transparent conductive thin film was quantitatively analyzed by an
ICP emission spectrometry (SPS4000, manufactured by Seiko
Instruments Co., Ltd.). (3) Crystallinity and orientation of the
film were studied by X-ray diffraction measurement using an X-ray
diffraction apparatus (M18XHF22, manufactured by Mac Science Co.,
Ltd.) utilizing CuK.alpha.-ray. (4) In addition, specific
resistance of each transparent conductive thin film was measured by
a four probe method using resistivity meter Roresta EP (MCP-T360
model, manufactured by Dia Instruments Co., Ltd.). (5) Still more,
total ray light transmittance and parallel ray transmittance, along
with total ray reflectivity and parallel ray reflectivity,
including the substrate, were measured using a spectrometer
(U-4000, manufactured by Hitachi, Ltd.) (6) Haze ratio of the film
was evaluated using a haze meter (HM-150, manufactured by Murakami
Color Research Laboratory), based on JIS K7136. Surface roughness
(RA) of the film was measured on a region of 5 cm.times.5 .mu.m
using an atomic force microscope (NS-III, D5000 system,
manufactured by Digital Instruments Co., Ltd.).
Examples 1 to 3
[0117] A zinc oxide-based transparent conductive film with large
surface irregularity was prepared as follows, using zinc oxide
sintered body targets (manufactured by Sumitomo Metal Mining Co.,
Ltd.) containing aluminum as an addition element.
[0118] Composition of the targets used was quantitatively analyzed
by an ICP emission spectrometry (SPS4000, manufactured by Seiko
Instruments Co., Ltd.), and was 0.30 to 0.65% by atom as
Al/(Zn+Al), as shown in Table 1. Any of the targets had a purity of
99.999% and a size of 6 inch (.PHI.).times.5 mm (thickness).
[0119] This sputtering target was attached at a cathode (maximum
horizontal magnetic field intensity, at the position apart from the
target surface by 1 cm, was about 80 kA/m (1 kG)) for ferromagnetic
target of a direct current magnetron sputtering apparatus (SPE503K,
manufactured by Tokki Corp.), and a Corning 7059 glass substrate
with a thickness of 1.1 mm was attached at the counterface surface
of said sputtering target. It should be noted that, average light
transmittance in a visible light wavelength region of the Corning
7059 glass substrate itself is 92%. Distance between the sputtering
target and the substrate was set at 50 mm.
[0120] Next, inside of the chamber was subjected to vacuuming, and
when vacuum degree thereof reached equal to or lower than
2.times.10.sup.-4 Pa, argon gas with a purity of 99.9999% by mass
was introduced into the chamber to set gas pressure at 3.0 Pa.
Substrate temperature was set at 400.degree. C., and a direct
current input power of 400 W (input power density to the
target=direct current input power/target surface area=400 W+181
cm.sup.2=2.210 W/cm.sup.2) was input between the target and the
substrate to generate direct current plasma. After performing
pre-sputtering for 10 minutes to clean the target surface, film
formation by sputtering was performed while holding the substrate
just above the center of the target. Because of high input power,
film formation speed was as high as 68 to 70 nm/min.
[0121] Film thickness of the resultant transparent conductive film,
composition, crystallinity of the film, orientation and specific
resistance of each transparent conductive film were measured by the
above-described methods. Still more, total ray light transmittance
and parallel ray transmittance, along with total ray reflectivity
and parallel ray reflectivity, including the substrate, and haze
ratio of the film were measured by the above-described methods.
[0122] In Table 1, characteristics of the films obtained in
Examples 1 to 3 are shown. Composition of the resultant film was
nearly the same as composition of the target. In addition, film
thickness was 830 to 850 nm. Surface roughness Ra measured with an
atomic force microscope showed as high as 35.2 to 56.1 nm, and haze
ratio was also as high as 8 to 12.5%, irrespective of the high film
formation speed of 68 to 70 nm/min. From a surface SEM photo of the
film of Example 2 shown in FIG. 4, it is understood that the film
is composed of a large grain and has large surface irregularity. It
was confirmed that the films of Example 1 and Example 3 also had
similar surface texture. In addition, surface resistance was 43 to
63 .OMEGA./.quadrature., showed high conductivity. Therefore, it
was confirmed from Examples 1 to 3 that the zinc oxide-based
transparent conductive film, having high haze ratio and superior
conductivity, can be obtained in high speed.
Comparative Examples 1 to 3
[0123] A zinc oxide-based transparent conductive film was prepared
from zinc oxide sintered body targets containing aluminum
similarly, except that target composition was changed from Examples
1 to 3. As the targets, one having a composition thereof of 1.59%
by atom (Comparative Example 1), 0.80% by atom (Comparative Example
2), and 0.20% by atom (Comparative Example 3) as Al/(Zn+Al), were
used. All conditions other than the composition of the target were
set the same as those in Examples 1 to 3.
[0124] In Table 1, characteristics of the resultant films are
shown. Composition of the resultant films was nearly the same as
composition of the target. In any cases, high film formation speed
of 66 to 70 nm/min was obtained, because input power density to the
target in film formation was set at same 2.210 W/cm.sup.2, as in
Examples 1 to 3. However, the films of Comparative Examples 1 and 2
had lower Ra value and lower haze ratio, different from those of
Examples 1 to 3, although having good conductivity. Therefore,
because of insufficient optical confinement effect, they cannot be
utilized as a surface transparent electrode of a highly efficient
solar cell. In addition, because the film of Comparative Example 3
had too high surface resistance, although having high Ra value and
haze ratio, it cannot be utilized as an electrode of a solar
cell.
Examples 4 to 6
[0125] Zinc oxide-based transparent conductive films with large
surface irregularity were prepared, using zinc oxide sintered body
targets containing gallium as an addition element. The zinc
oxide-based transparent conductive films were obtained under
similar condition as in Examples 1 to 3, except by using the zinc
oxide sintered body targets containing gallium, as target
composition of 1.74% by atom as Ga/(Zn+Ga) (Example 4), 0.87% by
atom (Example 5), and 0.30% by atom (Example 5), a gas pressure of
8.0 Pa, and a substrate temperature of 300.degree. C.
[0126] In Table 1, preparation condition of the films and
characteristics of the resultant films are shown. Composition of
the resultant films was nearly the same as composition of the
target. The films of Examples 4 to 6 had a film thickness of 780 to
800 nm and formed in a high speed of about 71 nm/min, however, any
of the Ra values of the films was as high as 48 to 56 nm, and also
the haze ratios were as high as 10.8 to 12.1%, and surface
resistances were within a range of 11 to 25 .OMEGA./.quadrature.,
showing high conductivity. Therefore, such films can be utilized
for the surface transparent electrode of the solar cell with
superior optical confinement effect.
Comparative Examples 4 to 6
[0127] Zinc oxide-based transparent conductive films were prepared
from zinc oxide sintered body targets containing gallium similarly
as in Examples 4 to 6, however, the targets with a target
composition of 3.48% by atom as Ga/(Zn+Ga) (Comparative Example 4),
2.62% by atom (Comparative Example 5), and 0.20% by atom
(Comparative Example 6) were used. High film formation speed of 70
to 72 nm/min was obtained, because input power density to the
target in film formation was also set at same 2.210 W/cm.sup.2 as
in Examples 1 to 3. Evaluation of the resultant films was performed
similarly as in Examples 1 to 3.
[0128] In Table 1, characteristics of the resultant films are
shown. Composition of the films was nearly the same as composition
of the targets. The films of Comparative Examples 4 and 5 had lower
Ra value and lower haze ratio, different from those of Examples 4
to 6, although having good conductivity. Therefore, because of
insufficient optical confinement effect, they cannot be utilized as
a surface transparent electrode of a highly efficient solar cell.
In addition, because the film of Comparative Example 6 had too high
surface resistance, although having high Ra value and haze ratio,
it cannot be utilized as an electrode of a solar cell.
Examples 7 to 10
[0129] Zinc oxide-based transparent conductive films with large
surface irregularity were prepared, using zinc oxide sintered body
targets containing aluminum and gallium as addition elements. The
zinc oxide-based transparent conductive films were obtained under
similar condition as in Examples 1 to 3, except by using the zinc
oxide sintered body targets containing aluminum and gallium, with
target compositions shown in Table 1, a gas pressure of 5.0 Pa, and
a substrate temperature of 350.degree. C. In addition, evaluation
of the resultant films was performed similarly as in Examples 1 to
3.
[0130] In Table 1, preparation condition of the films and
characteristics of the resultant films are shown. Composition of
the resultant films was nearly the same as composition of the
target. The films of Examples 7 to 10 had a film thickness of 824
to 851 nm and formed in a high speed of about 69 nm/min, however,
any of the Ra values of the films was as high as 38 to 50 nm, and
also the haze ratios were as high as 8.5 to 12.1%, and surface
resistances were within a range of 29 to 57 .OMEGA./.quadrature.,
showing high conductivity. Therefore, such films can be utilized
for the surface transparent electrode of the solar cell with
superior optical confinement effect.
Comparative Examples 7 to 9
[0131] Zinc oxide-based transparent conductive films were prepared
from zinc oxide sintered body targets containing aluminum and
gallium similarly as in Examples 7 to 10, however, the targets with
compositions of outside the composition range of the present
invention, as shown in Table 1, were used. The zinc oxide-based
transparent conductive films were prepared all under the same
condition as in Examples 7 to 10, other than the target
compositions. High film formation speed of 66 to 70 nm/min was
obtained, because input power density to the target in film
formation was also set at 2.210 W/cm.sup.2, the same as in Examples
7 to 10. Evaluation of the resultant films was performed similarly
as in Examples 1 to 3.
[0132] In Table 1, characteristics of the resultant films are
shown. Composition of the films was nearly the same as composition
of the targets. The films of Comparative Examples 7 and 8 had lower
Ra value and lower haze ratio, different from those of Examples 7
to 10, although having good conductivity. Therefore, because of
insufficient optical confinement effect, they cannot be utilized as
a surface transparent electrode of a highly efficient solar cell.
In addition, because the film of Comparative Example 9 had too high
surface resistance, although having high Ra value and haze ratio,
it cannot be utilized as an electrode of a solar cell.
Comparative Examples 10 to 13
[0133] Zinc oxide-based transparent conductive films were prepared
from zinc oxide sintered body targets containing aluminum similarly
as in Examples 1 to 3, however, the target with a target
composition of 3.16% by atom as Al/(Zn+Al) was used. This target
composition was also used in NON-PATENT DOCUMENT 2. Input power
density to the target in film formation was changed within a range
of 0.442 to 2.210 W/cm.sup.2. The Zinc oxide-based transparent
conductive films with a film composition of 3.18% by atom as
Al/(Zn+Al) were prepared by performing film formation all under the
same condition as in Examples 1 to 3, other than the target
composition and input power. Characteristics evaluation of the
resultant films was performed similarly as in Examples 1 to 3.
[0134] In Table 1, characteristics of the resultant films are
shown. With increase in input power density to the target in film
formation, film formation speed was increased. As shown in
Comparative Example 10, in the case of low power charge of a input
power to the target of 0.442 W/cm.sup.2, the transparent conductive
film with high Ra value and haze ratio, as well as satisfactory
conductivity was obtained, and the same result as in NON-PATENT
DOCUMENT 2 was obtained. However, in Comparative Example 10,
because of low input power density, film formation speed was
significantly slow and it thus is not practical. Comparative
Examples 11 to 13 are examples in which input power density was
increased further, however, with increase in input power density,
haze ratio decreased significantly, and in 1.105 W/cm.sup.2
(Comparative Example 11), a film with high haze ratio was not
obtained.
Comparative Examples 14 to 17
[0135] Zinc oxide-based transparent conductive films were prepared
from zinc oxide sintered body targets containing gallium similarly
as in Examples 4 to 6. Film formation was performed under the same
condition as in Examples 4 to 6, except by using a target with a
target composition of 4.99% by atom as Ga/(Zn+Ga), a film formation
gas pressure of 8.3 Pa, and by changing input power density to the
target in film formation within a range of 0.442 to 2.210
W/cm.sup.2. Zinc oxide-based transparent conductive films with a
film composition of 5.03% by atom as Ga/(Zn+Ga) was obtained.
Characteristics evaluation of the resultant films was performed
similarly as in Examples 1 to 3.
[0136] In Table 1, characteristics of the resultant films are
shown. With increase in input power density to the target in film
formation, film formation speed increased, and Ra value and haze
ratio of the film showed decreasing tendency. However, in any of
the input power density, a film with high haze ratio, which can be
utilized as the surface transparent electrode of the solar cell,
was not obtained.
Examples 11 to 13 and Comparative Example 18
[0137] Zinc oxide-based transparent conductive films were prepared
from zinc oxide sintered body targets containing gallium similarly
as in Examples 4 to 6. The zinc oxide-based transparent conductive
films, having a film thickness of 830 nm (Comparative Example 18),
1010 nm (Example 11), 1350 nm (Example 12), and 1620 nm (Example
13), were prepared using a target with a target composition of
1.31% by atom as Ga/(Zn+Ga), a film formation gas pressure of 5.5
Pa, and changing input power density to the target of 2.760
W/cm.sup.2, and by changing film formation time. Characteristics
evaluation of the resultant films was performed similarly as in
Examples 1 to 3.
[0138] In Table 1, characteristics of the resultant films are
shown. Composition of any of the films was 1.35% by atom as
Ga/(Zn+Ga), nearly the same as composition of the targets. With
increase in film thickness, surface resistance decreased, but Ra
value and haze ratio also increased. The film of Comparative
Example 18, although having sufficiently low surface resistance,
had low haze ratio and weak optical confinement effect, therefore,
it cannot be utilized as a surface transparent electrode of a
highly efficient solar cell. However, because the films of Examples
11 to 13 have not only the low surface resistance but also the
sufficiently high haze ratio of equal to or higher than 8%, they
can be utilized as the surface transparent electrode of the highly
efficient solar cell.
Examples 14 to 16 and Comparative Examples 19 to 20
[0139] Zinc oxide-based transparent conductive films were prepared
from zinc oxide sintered body targets containing aluminum and
gallium similarly as in Examples 7 to 10. The zinc oxide-based
transparent conductive films were prepared under condition of a
target composition of 0.28% by atom as Ga/(Zn+Ga), 0.28% by atom as
Al/(Zn+Al), a input power density to the target of 1.660
W/cm.sup.2, and a substrate temperature of 300.degree. C., and by
changing gas pressure so as to be 1.0 Pa (Comparative Example 19),
2.0 Pa (Example 14), 10.5 Pa (Example 15), 15.0 Pa (Example 16),
and 20.0 Pa (Comparative Example 20). The zinc oxide-based
transparent conductive films with approximately the same film
thickness of 1340 to 1360 nm were prepared, by adjusting film
formation time, in consideration of film formation speed under each
gas pressure. Evaluation of the resultant films was performed
similarly as in Examples 1 to 3.
[0140] In Table 1, film formation condition and characteristics of
the resultant films are shown. Composition of the films was nearly
the same as composition of the target. With increase in gas
pressure, Ra value and haze ratio increased. The film of
Comparative Example 19 had low haze ratio and weak optical
confinement effect, therefore, it cannot be utilized as a surface
transparent electrode of a highly efficient solar cell. The
resultant film in Comparative Example 20 had very slow film
formation speed in preparation and thus poor productivity, as well
as high surface resistance and weak adhesive strength of the film
to the substrate and thus is easily peeled, although having high
haze ratio, therefore, it cannot be utilized as an electrode of a
device. However, because the films of Examples 14 to 16 had not
only the low surface resistance but also the sufficiently high haze
ratio of equal to or higher than 8%, and high adhesive strength of
the film, they can be utilized as the surface transparent electrode
of the highly efficient solar cell.
Examples 17 to 19 and Comparative Examples 21 to 22
[0141] Zinc oxide-based transparent conductive films were prepared
from zinc oxide sintered body targets containing gallium similarly
as in Examples 4 to 6. The zinc oxide-based transparent conductive
films were prepared, under condition of a target composition of
0.30% by atom as Ga/(Zn+Ga), a input power density to the target of
2.760 W/cm.sup.2, and a gas pressure of 6.0 Pa, and by changing a
substrate temperature so as to be 150.degree. C. (Comparative
Example 21), 200.degree. C. (Example 17), 400.degree. C. (Example
18), 500.degree. C. (Example 19) and 600.degree. C. (Comparative
Example 22). The zinc oxide-based transparent conductive films with
a film thickness of 1005 to 1012 nm were prepared, by adjusting
film formation time, in consideration of different film formation
speed at each film formation temperature. Characteristics
evaluation of the resultant films was performed similarly as in
Examples 1 to 3.
[0142] In Table 1, film formation condition and characteristics of
the resultant films are shown. Composition of any of the films was
0.31% by atom as Ga/(Zn+Ga), nearly the same as composition of the
target. With increase in substrate temperature, Ra value and haze
ratio also increased, but surface resistance also increased. The
film of Comparative Example 21, although having sufficiently low
surface resistance, had low haze ratio and weak optical confinement
effect, therefore, it cannot be utilized as a surface transparent
electrode of a highly efficient solar cell. The resultant film of
Comparative Example 22 had very slow film formation speed in
preparation and thus poor productivity, as well as high surface
resistance, although having high haze ratio, and thus cannot be
utilized as the transparent electrode of the solar cell. However,
because the films of Examples 17 to 19 have not only the low
surface resistance but also the sufficiently high haze ratio of
equal to or higher than 8%, they can be utilized as the surface
transparent electrode of the highly efficient solar cell
Examples 20 to 26
[0143] According to the following procedure, a transparent
conductive film with large surface irregularity having a structure,
in which the Zinc oxide-based transparent conductive film was
formed on the indium oxide-based transparent conductive film
containing tin, was prepared by a sputtering method.
[0144] Composition of the targets used in preparation of the indium
oxide-based transparent conductive film of the base, was
quantitatively analyzed by an ICP emission spectrometry (SPS4000,
manufactured by Seiko Instruments Co., Ltd.), and was 9.29% by atom
as Sn/(In+Sn), as shown in Table 2. The targets had a purity of
99.999% and a size of 6 inch (.PHI.).times.5 mm (thickness). Film
formation was performed using an apparatus used in the zinc
oxide-based transparent conductive films of Examples 1 to 19, and
also with the same cathode type. A Corning 7059 glass substrate
with a thickness of 1.1 mm was attached at the counterface surface
of the target. It should be noted that average light transmittance
in a visible light wavelength region of the Corning 7059 glass
substrate itself is 92%. Distance between the sputtering target and
the substrate was set at 50
[0145] When vacuum degree in a chamber reached equal to or lower
than 2.times.10.sup.-4 Pa, argon gas mixed with 6% by volume of
O.sub.2 gas was introduced into the chamber to set gas pressure at
0.6 Pa, and while heating the substrate temperature up to
300.degree. C., a direct current input power of 300 W (input power
density to the target=direct current input power/target surface
area=300 W/181 sq=1.660 W/cm.sup.2) was input between the target
and the substrate to generate direct current plasma. After
performing pre-sputtering for 10 minutes to clean the target
surface, film formation by sputtering was performed while holding
the substrate just above the center of the target, to form the
indium oxide-based transparent conductive film with a film
thickness of 150 nm. It should be noted that, the indium
oxide-based transparent conductive film prepared by this method is
a crystalline film, having a surface roughness of 1.32 nm.
[0146] On this indium oxide-based transparent conductive film, zinc
oxide-based transparent conductive film was formed as described in
follows. That is, in Example 20, the zinc oxide-based transparent
conductive film was formed similarly as in Example 1; in Example
21, the zinc oxide-based transparent conductive film was formed
similarly as in Example 3; in Example 22, the zinc oxide-based
transparent conductive film was formed similarly as in Example 4;
in Example 23, the zinc oxide-based transparent conductive film was
formed similarly as in Example 6; in Example 24, the zinc
oxide-based transparent conductive film was formed similarly as in
Example 7; in Example 25, the zinc oxide-based transparent
conductive film was formed similarly as in Example 9; and in
Example 26, the zinc oxide-based transparent conductive film was
formed similarly as in Example 10; to obtain the transparent
conductive film laminated bodies. Compositions thereof are shown in
Table 2. As characteristics evaluation of the transparent
conductive film laminated bodies prepared, evaluation of pole
figure was also performed by X-ray diffraction measurement (X'Pert
Pro MPD, manufactured by PANalytical Co., Ltd.), in addition to
similar items performed in the zinc oxide-based transparent
conductive films of Examples 1 to 3, to evaluate by how much degree
the c-axis of the zinc oxide-based transparent conductive film is
inclined relative to a vertical direction of the substrate.
[0147] In Table 2, characteristics evaluation results of the
transparent conductive film laminated bodies of Examples 20 to 26
are shown. Film composition of any of the indium oxide-based
transparent conductive film of the base, was nearly the same as
composition of the target, and as for film formation speed of the
zinc oxide-based transparent conductive film, nearly the same high
film formation speed as in not inserting the indium oxide-based
transparent conductive film as the base, was attained. The
resultant transparent conductive film laminated bodies had
extremely decreased surface resistance as compared with the case of
not inserting the indium oxide-based transparent conductive film as
the base. Surface roughness and haze ratio of the transparent
conductive film laminated bodies of Examples 20 to 26 showed
somewhat decreasing tendency as compared with the case of not
inserting the indium oxide-based transparent conductive film as the
base, however, showed sufficiently high value in utilizing as the
surface transparent electrode of the solar cell. The c-axis of the
zinc oxide-based transparent conductive film was inclined by equal
to or smaller than 15 degree relative to a vertical direction of
the substrate.
[0148] Such films can be utilized for the surface transparent
electrode of the solar cell with superior optical confinement
effect.
Comparative Examples 23 to 26
[0149] Similarly as in Examples 20 to 26, on the indium oxide-based
transparent conductive film as the base, the zinc oxide-based
transparent conductive film was formed as described in follows to
prepare the transparent conductive film laminated bodies. That is,
in Comparative Example 23, the zinc oxide-based transparent
conductive film was formed similarly as in Comparative Example 2;
in Comparative Example 24, the zinc oxide-based transparent
conductive film was formed similarly as in Comparative Example 3;
in Comparative Example 25, the zinc oxide-based transparent
conductive film was formed similarly as in Comparative Example 8;
and in Comparative Example 26, the zinc oxide-based transparent
conductive film was formed similarly as in Comparative Example 9;
to obtain the transparent conductive film laminated bodies.
Compositions thereof are shown in Table 2. As characteristics
evaluation of the transparent conductive film laminated bodies
prepared, evaluation of pole figure was also performed by X-ray
diffraction measurement, similarly as in the zinc oxide-based
transparent conductive films of Examples 1 to 3.
[0150] In Table 2, characteristics evaluation results of the
transparent conductive film laminated bodies of Comparative
Examples 23 to 26 are shown. The transparent conductive film
laminated bodies of Comparative Examples 23 to 26 had decreased
surface resistance as compared with the case of not inserting the
indium oxide-based transparent conductive film as the base,
however, showed tendency of having a surface roughness Ra value and
haze ratio of the transparent conductive film laminated bodies
equal to or lower than as compared with the case of not inserting
the indium oxide-based transparent conductive film, as the base.
The transparent conductive film laminated bodies of Comparative
Examples 23 and 25 showed low haze ratio and weak optical
confinement effect, although having sufficiently low surface
resistance, and thus cannot be utilized as the surface transparent
electrode of the highly efficient solar cell. The transparent
conductive film laminated bodies of Comparative Examples 24 and 26
had extremely high surface resistance, and thus cannot be utilized
as the surface transparent electrode of the highly efficient solar
cell. Therefore, these films cannot be utilized for the surface
transparent electrode of the solar cell with superior optical
confinement effect.
Examples 27 to 33
[0151] The indium oxide-based transparent conductive film of the
base, shown in Examples 20 to 26, was prepared under the same
condition, except by changing to a method for film formation
without heating the substrate and then annealing under vacuum,
instead of film formation under heating. Annealing condition was
set at 300 to 400.degree. C. for 30 to 60 minutes in vacuum, as
shown in Table 2. It should be noted that, the indium oxide-based
transparent conductive film prepared by this method is a
crystalline film in any case, having a surface roughness of 1.3 to
2.1 nm.
[0152] On this indium oxide-based transparent conductive film, zinc
oxide-based transparent conductive film described as described in
follows was formed. That is, in Example 27, the zinc oxide-based
transparent conductive film was formed similarly as in Example 1;
in Example 28, the zinc oxide-based transparent conductive film was
formed similarly as in Example 3; in Example 29, the zinc
oxide-based transparent conductive film was formed similarly as in
Example 4; in Example 30, the zinc oxide-based transparent
conductive film was formed similarly as in Example 6; in Example
31, the zinc oxide-based transparent conductive film was formed
similarly as in Example 7; in Example 32, the zinc oxide-based
transparent conductive film was formed similarly as in Example 9;
and in Example 33, the zinc oxide-based transparent conductive film
was formed similarly as in Example 10 to obtain the transparent
conductive film laminated bodies. Compositions thereof are shown in
Table 2. As characteristics evaluation of the transparent
conductive film laminated bodies prepared, evaluation of pole
figure was also performed by X-ray diffraction measurement, in
addition to similar items performed in the zinc oxide-based
transparent conductive films of Examples 1 to 3.
[0153] In Table 2, characteristics evaluation results of the
transparent conductive film laminated bodies of Examples 27 to 33
are shown. Film composition of any of the indium oxide-based
transparent conductive film of the base, was nearly the same as
composition of the target, and as for film formation speed of the
zinc oxide-based transparent conductive film, nearly the same high
film formation speed as in not inserting the indium oxide-based
transparent conductive film as the base, was attained. As shown in
Table 2, the transparent conductive film laminated bodies had
extremely decreased surface resistance as compared with the case of
not inserting the indium oxide-based transparent conductive film as
the base, and had increased surface roughness Ra value and haze
ratio as well.
[0154] From comparisons between Example 20 and Example 27, Example
21 and Example 28, Example 22 and Example 29, Example 23 and
Example 30, Example 24 and Example 31, Example 25 and Example 32,
along with Example 26 and Example 33, it is understood that the
case of using the indium oxide-based transparent conductive film,
which was subjected to annealing treatment after film formation
without heating the substrate, as the base, (Examples 27 to 33)
provides a film with increased surface roughness Ra value and haze
ratio, as compared with the case of using the indium oxide-based
transparent conductive film obtained by film formation under
heating, as the base, (Examples 20 to 26).
[0155] Therefore, such transparent conductive film laminated bodies
can be utilized for the surface transparent electrode of the solar
cell with superior optical confinement effect.
Comparative Examples 27 to 30
[0156] By a similar procedure as in Examples 27 to 33, the
transparent conductive film laminated bodies were prepared, and
composition thereof was set as follows. That is, in Comparative
Example 27, the zinc oxide-based transparent conductive film was
formed similarly as in Comparative Example 2, on the indium
oxide-based transparent conductive film formed under condition of
Examples 27 to 28; in Comparative Example 28, the zinc oxide-based
transparent conductive film of Comparative Example 3 was formed, on
the indium oxide-based transparent conductive film formed under
condition of Examples 27 to 28; in Comparative Example 29, the zinc
oxide-based transparent conductive film of Comparative Example 5
was formed, on the indium oxide-based transparent conductive film
formed under condition of Examples 29 to 30; and in Comparative
Example 30, the zinc oxide-based transparent conductive film of
Comparative Example 6 was formed, on the indium oxide-based
transparent conductive film formed under condition of Examples 27
to 28; to obtain the transparent conductive film laminated bodies.
As characteristics evaluation of the transparent conductive film
laminated bodies prepared, evaluation of pole figure was also
performed by X-ray diffraction measurement, in addition to similar
items performed in the zinc oxide-based transparent conductive
films of Examples 1 to 3.
[0157] In Table 2, characteristics evaluation results of the
transparent conductive film laminated bodies of Comparative
Examples 27 to 30 are shown. The transparent conductive film
laminated bodies of Comparative Examples 27 to 30 had decreased
surface resistance as compared with the case of not inserting the
indium oxide-based transparent conductive film, as the base.
However, the transparent conductive film laminated bodies of
Comparative Examples 27 and 29 had low haze ratio and weak optical
confinement effect, although having sufficiently low surface
resistance, and thus cannot be utilized as the surface transparent
electrode of the highly efficient solar cell. The transparent
conductive film laminated bodies of Comparative Examples 28 and 30
had extremely high surface resistance, although having increased Ra
value and haze ratio, and thus cannot be utilized as the surface
transparent electrode of the solar cell. Therefore, such films
cannot be utilized for the surface transparent electrode of the
highly efficient solar cell.
Examples 34 to 37 and Comparative Example 31
[0158] The transparent conductive film laminated bodies were
prepared by changing composition of the indium oxide-based
transparent conductive film used as the base of Examples 27 to 33.
As shown in Table 2, target composition in preparing the indium
oxide-based transparent conductive film was changed within a range
of 0.20 to 17.56% by atom as Sn/(In+Sn). As film formation
condition, film formation gas pressure was set at 0.3 Pa, argon gas
mixed with 8% by volume of oxygen was used as film formation gas,
and annealing was performed at 200.degree. C. for 30 minutes in
vacuum, after film formation without heating the substrate.
Composition of any of the base films obtained by this method was
nearly equal to the target composition, as shown in Table 2. As for
crystallinity of the film, in the case of Sn/(In+Sn) is 17.56% by
atom (Comparative Example 31), it was a mixed film of crystalline
and amorphous substances, but in the case where it is 0.20 to
14.95% by atom (Examples 34 to 37), it was a completely crystalline
film. On this base film prepared in this way, the zinc oxide-based
transparent conductive film of Example 17 was formed. As for film
formation speed of the zinc oxide-based transparent conductive
film, nearly the same high film formation speed as in not inserting
the indium oxide-based transparent conductive film, as the base,
was attained. Compositions thereof are shown in Table 2. As
characteristics evaluation of the transparent conductive film
laminated bodies prepared, evaluation of pole figure was also
performed by X-ray diffraction measurement, in addition to similar
items performed in the zinc oxide-based transparent conductive
films of Examples 1 to 3.
[0159] In Table 2, characteristics evaluation results of the
transparent conductive film laminated bodies are shown. Any of the
transparent conductive film laminated bodies had nearly the same or
smaller surface resistance, as compared with the case of not
inserting the indium oxide-based transparent conductive film, as
the base, showing sufficient conductivity. As for surface roughness
Ra value and haze ratio of the laminated bodies, increasing
tendency was observed by inserting the base film, in Examples 34 to
37, however, they decreased significantly in Comparative Examples
31. Reason for decrease in the Ra value and haze ratio in
Comparative Examples 31 is that the base film was not a complete
crystalline film.
[0160] Examples 34 to 37 showed sufficiently high values for
enabling to be utilized as the surface transparent electrode of the
solar cell with superior optical confinement effect. However,
Comparative Examples 31 cannot be utilized for that object, because
of having small haze ratio.
Examples 38 to 44
[0161] The transparent conductive film laminated bodies were
prepared by changing the tin-containing indium oxide-based
transparent conductive film, used as the base film in Examples 20
to 26, to titanium-containing indium oxide-based transparent
conductive film. The indium oxide-based transparent conductive film
of the base, was prepared under the following condition.
[0162] Composition of the targets used in preparation of the indium
oxide-based transparent conductive film of the base, was
quantitatively analyzed by an ICP emission spectrometry (SPS4000,
manufactured by Seiko Instruments Co., Ltd.), and was 1.73% by atom
as Ti/(In+Ti), as shown in Table 3. The target had a purity of
99.999% and a size of 6 inch (.PHI.).times.5 mm (thickness).
[0163] Film formation was performed using an apparatus used in the
zinc oxide-based transparent conductive films of Examples 20 to 26,
and also with the same cathode type. A Corning 7059 glass substrate
with a thickness of 1.1 mm was attached at the counterface surface
of the target. It should be noted that, average light transmittance
in a visible light wavelength region of the Corning 7059 glass
substrate itself is 92%. It should be noted that, distance between
the sputtering target and the substrate was set at 50 mm. When
vacuum degree inside a chamber reached equal to or lower than
2.times.10.sup.-4 Pa, argon gas mixed with 6% by volume of O.sub.2
gas was introduced into the chamber to set gas pressure at 0.4 Pa,
and after heating the substrate up to 300.degree. C., a direct
current input power of 300 W (input power density to the
target=direct current input power/target surface area=300 W/181
cm.sup.2=1.660 W/cm.sup.2) was input between the target and the
substrate to generate direct current plasma. After performing
pre-sputtering for 10 minutes to clean the target surface, film
formation by sputtering was performed while holding the substrate
just above the center of the target to form the indium oxide-based
transparent conductive film, with a film thickness of 200 nm, on
the substrate. It should be noted that, the indium oxide-based
transparent conductive film prepared by this method was a
crystalline film having a surface roughness Ra of 1.80 nm.
[0164] On this indium oxide-based transparent conductive film, zinc
oxide-based transparent conductive film was formed as described in
follows. That is, in Example 38, the zinc oxide-based transparent
conductive film was formed similarly as in Example 1; in Example
39, the zinc oxide-based transparent conductive film was formed
similarly as in Example 3; in Example 40, the zinc oxide-based
transparent conductive film was formed similarly as in Example 4;
in Example 41, the zinc oxide-based transparent conductive film was
formed similarly as in Example 6; in Example 42, the zinc
oxide-based transparent conductive film was formed similarly as in
Example 7; in Example 43, the zinc oxide-based transparent
conductive film was formed similarly as in Example 9; and in
Example 44, the zinc oxide-based transparent conductive film was
formed similarly as in Example 10 to obtain the transparent
conductive film laminated bodies. Compositions thereof are shown in
Table 3. As characteristics evaluation of the transparent
conductive film laminated bodies prepared, evaluation of pole
figure was also performed by X-ray diffraction measurement, in
addition to similar items performed in the zinc oxide-based
transparent conductive films of Examples 1 to 3.
[0165] In Table 3, characteristics evaluation results of the
transparent conductive film laminated bodies of Examples 38 to 44
are shown. In any case, film composition of the indium oxide-based
transparent conductive film of the base, was nearly the same as
composition of the target, and as for film formation speed of the
zinc oxide-based transparent conductive film, nearly the same high
film formation speed as in not inserting the indium oxide-based
transparent conductive film, as the base, was attained. As shown in
Table 3, the transparent conductive film laminated bodies had
extremely decreased surface resistance as compared with the case of
not inserting the indium oxide-based transparent conductive film,
as the base. Surface roughness Ra value and haze ratio of the
transparent conductive film laminated bodies of Examples 38 to 44
showed somewhat decreasing tendency as compared with the case of
not inserting the indium oxide-based transparent conductive film,
as the base, however, showed sufficiently high value in utilizing
as the surface transparent electrode of the solar cell. Therefore,
such films can be utilized for the surface transparent electrode of
the solar cell with superior optical confinement effect.
Comparative Examples 32 to 35
[0166] On the indium oxide-based transparent conductive film
prepared in Examples 38 to 44, as the base, the zinc oxide-based
transparent conductive films were formed as described in follows to
prepare the transparent conductive film laminated bodies. That is,
in Comparative Example 32, the zinc oxide-based transparent
conductive film was formed similarly as in Comparative Example 2;
in Comparative Example 33, the zinc oxide-based transparent
conductive film was formed similarly as in Comparative Example 3;
in Comparative Example 34, the zinc oxide-based transparent
conductive film was formed similarly as in Comparative Example 8;
and in Comparative Example 35, the zinc oxide-based transparent
conductive film was formed similarly as in Comparative Example 9;
to obtain the transparent conductive film laminated bodies.
Compositions thereof are shown in Table 3. As characteristics
evaluation of the transparent conductive film laminated bodies
prepared, evaluation of pole figure was also performed by X-ray
diffraction measurement, in addition to similar items performed in
the zinc oxide-based transparent conductive films of Examples 1 to
3.
[0167] In Table 3, characteristics evaluation results of the
transparent conductive film laminated bodies of Comparative
Examples 32 to 35 are shown. The transparent conductive film
laminated bodies had decreased surface resistance as compared with
the case of not inserting the indium oxide-based transparent
conductive film, as the base, however, showed tendency of having a
surface roughness Ra value and haze ratio of the transparent
conductive film laminated bodies equal to or lower as compared with
the case of not inserting the indium oxide-based transparent
conductive film, as the base. The transparent conductive film
laminated bodies of Comparative Examples 32 and 34 showed low haze
ratio and weak optical confinement effect, although having
sufficiently low surface resistance, and thus cannot be utilized as
the surface transparent electrode of the highly efficient solar
cell. The transparent conductive film laminated bodies of
Comparative Examples 33 and 35 had extremely high surface
resistance, although having high Ra value and haze ratio, and thus
cannot be utilized as the surface transparent electrode of the
highly efficient solar cell. Therefore, such films cannot be
utilized for the surface transparent electrode of the highly
efficient solar cell.
Examples 45 to 51
[0168] The indium oxide-based transparent conductive film, as the
base in Examples 38 to 44, was prepared under the same condition,
except by changing to a method for film formation without heating
the substrate and then annealing under vacuum, instead of film
formation under heating. Annealing condition was set at 300 to
400.degree. C. for 30 to 60 minutes in vacuum, as shown in Table 3.
It should be noted that, the indium oxide-based transparent
conductive film prepared by this method is a crystalline film in
any case, having a surface roughness of 1.15 to 1.51 nm.
[0169] On this indium oxide-based transparent conductive film, zinc
oxide-based transparent conductive film was formed as described in
follows. That is, in Example 45, the zinc oxide-based transparent
conductive film was formed similarly as in Example 1; in Example
46, the zinc oxide-based transparent conductive film was formed
similarly as in Example 3; in Example 47, the zinc oxide-based
transparent conductive film was formed similarly as in Example 4;
in Example 48, the zinc oxide-based transparent conductive film was
formed similarly as in Example 6; in Example 49, the zinc
oxide-based transparent conductive film was formed similarly as in
Example 7; in Example 50, the zinc oxide-based transparent
conductive film was formed similarly as in Example 9; and in
Example 51, the zinc oxide-based transparent conductive film was
formed similarly as in Example 10 to obtain the transparent
conductive film laminated bodies. These compositions are shown in
Table 2 (3). As characteristics evaluation of the transparent
conductive film laminated bodies prepared, evaluation of pole
figure was also performed by X-ray diffraction measurement, in
addition to similar items performed in the zinc oxide-based
transparent conductive films of Examples 1 to 3.
[0170] In Table 3, characteristics evaluation results of the
transparent conductive film laminated bodies of Examples 45 to 51
are shown. In any case, film composition of the indium oxide-based
transparent conductive film of the base, was nearly the same as
composition of the target, and as for film formation speed of the
zinc oxide-based transparent conductive film, nearly the same high
film formation speed as in not inserting the indium oxide-based
transparent conductive film, as the base, was attained. In
addition, as shown in Table 3, the transparent conductive film
laminated bodies of Examples 45 to 51 had extremely decreased
surface resistance as compared with the case of not inserting the
indium oxide-based transparent conductive film, as the base, and
had increased surface roughness Ra value and haze ratio as
well.
[0171] In addition, from comparisons between Example 38 and Example
45, Example 39 and Example 46, Example 40 and Example 47, Example
41 and Example 48, Example 42 and Example 49, Example 43 and
Example 50, along with Example 44 and Example 51, it is understood
that the case of using the indium oxide-based transparent
conductive film, which was subjected to annealing treatment after
film formation without heating the substrate, as the base,
(Examples 45 to 51) provides a film with increased surface
roughness Ra value and haze ratio, as compared with the case of
using the indium oxide-based transparent conductive film obtained
by film formation under heating, as the base, (Examples 38 to
44).
[0172] Therefore, such films can be utilized for the surface
transparent electrode of the solar cell with superior optical
confinement effect.
Comparative Examples 36 to 39
[0173] By a similar procedure as in Examples 45 to 51, the
transparent conductive film laminated bodies were prepared, and
composition thereof was set as described follows. That is, in
Comparative Example 36, the zinc oxide-based transparent conductive
film was formed similarly as in Comparative Example 2, on the
indium oxide-based transparent conductive film formed under
condition of Examples 45 to 51; in Comparative Example 37, the zinc
oxide-based transparent conductive film of Comparative Example 3
was formed, on the indium oxide-based transparent conductive film
formed under condition of Examples 45 to 51; in Comparative Example
38, the zinc oxide-based transparent conductive film of Comparative
Example 5 was formed, on the indium oxide-based transparent
conductive film formed under condition of Examples 45 to 51; and in
Comparative Example 39, the zinc oxide-based transparent conductive
film of Comparative Example 6 was formed, on the indium oxide-based
transparent conductive film formed under condition of Examples 45
to 51; to obtain the transparent conductive film laminated bodies.
As characteristics evaluation of the transparent conductive film
laminated bodies prepared, evaluation of pole figure was also
performed by X-ray diffraction measurement, in addition to
similarly performing evaluation as in the zinc oxide-based
transparent conductive films of Examples 1 to 3.
[0174] In Table 3, characteristics evaluation results of the
transparent conductive film laminated bodies of Comparative
Examples 36 to 39 are shown. The transparent conductive film
laminated bodies had decreased surface resistance as compared with
the case of not inserting the indium oxide-based transparent
conductive film, as the base. However, the transparent conductive
film laminated bodies of Comparative Examples 36 and 38 had low
haze ratio and weak optical confinement effect, although having
sufficiently low surface resistance, and thus cannot be utilized as
the surface transparent electrode of the highly efficient solar
cell. The transparent conductive film laminated bodies of
Comparative Examples 37 and 39 had extremely high surface
resistance, although having increased Ra value and haze ratio, and
thus cannot be utilized as the surface transparent electrode of the
solar cell. Therefore, such films cannot be utilized for the
surface transparent electrode of the highly efficient solar
cell.
Examples 52 to 55 and Comparative Example 40
[0175] The transparent conductive film laminated bodies were
prepared by changing composition of the indium oxide-based
transparent conductive film, used as the base of Examples 45 to 51.
As shown in Table 3, target composition in preparing the indium
oxide-based transparent conductive film was changed within a range
of 0.35 to 7.25% by atom as Ti/(In+Ti). As film formation
condition, film formation gas pressure was set at 0.3 Pa, argon gas
mixed with 7% by volume of oxygen was used as film formation gas,
and annealing was performed at 300.degree. C. for 30 minutes in
vacuum, after film formation without heating the substrate.
Composition of any of the base films obtained by this method was
nearly equal to the target composition. As for crystallinity of the
film, in the case of Ti/(In+Ti) is 7.25% by atom (Comparative
Example 40), it was a mixed film of crystalline and amorphous
substances, but in the case where it is 0.35 to 5.50% by atom
(Examples 52 to 55), it was a completely crystalline film. On this
base film with a film thickness of 100 nm, prepared in this way,
the zinc oxide-based transparent conductive film was formed
similarly as in Example 14. As for film formation speed of the zinc
oxide-based transparent conductive film, nearly the same high film
formation speed as in not inserting the indium oxide-based
transparent conductive film, as the base, was attained.
Compositions thereof are shown in Table 3. As characteristics
evaluation of the transparent conductive film laminated bodies
prepared, evaluation of pole figure was also performed by X-ray
diffraction measurement, in addition to similar items performed in
the zinc oxide-based transparent conductive films of Examples 1 to
3.
[0176] In Table 3, characteristics evaluation results of the
transparent conductive film laminated bodies are shown. Any of the
transparent conductive film laminated bodies had nearly the same or
smaller surface resistance, as compared with the case of not
inserting the indium oxide-based transparent conductive film, as
the base, showing sufficient conductivity. As for surface roughness
Ra value and haze ratio of the laminated bodies, increasing
tendency was observed by inserting the base film, in Examples 52 to
55, however, they decreased significantly in Comparative Examples
40. Reason for decrease in the Ra value and haze ratio in
Comparative Examples 40 is that the base film was not a complete
crystalline film.
[0177] Examples 52 to 55 showed sufficiently high values for
enabling to be utilized as the surface transparent electrode of the
solar cell with superior optical confinement effect. However,
Comparative Examples 40 cannot be utilized for that object, because
of having small haze ratio.
Examples 56 to 59 and Comparative Example 41
[0178] The transparent conductive film laminated bodies were
prepared by using a tungsten-containing indium oxide-based
transparent conductive film, as the base, and forming the zinc
oxide-based transparent conductive film thereon. The indium
oxide-based transparent conductive film of the base, was prepared
by the following condition.
[0179] As shown in Table 4, target composition in preparing the
indium oxide-based transparent conductive film was changed within a
range of 0.30 to 5.01% by atom as W/(In+W). As film formation
condition, film formation gas pressure was set at 0.3 Pa, argon gas
mixed with 7% by volume of oxygen was used as film formation gas, a
direct current power of 400 W was input, and annealing was
performed at 300.degree. C. for 30 minutes in vacuum, after film
formation without heating the substrate. Composition of the base
films obtained by this method was nearly equal to the target
composition in any case. As for crystallinity of the film, in the
case of W/(In+W) is 5.01% by atom (Comparative Example 41), it was
a mixed film of crystalline and amorphous substances, but in the
case where it is 0.30 to 4.28% by atom (Examples 56 to 59), it was
a completely crystalline film. On this base film with a film
thickness of 180 nm, prepared in this way, the zinc oxide-based
transparent conductive film of Example 6 was formed. As for film
formation speed of the zinc oxide-based transparent conductive
film, nearly the same high film formation speed as in not inserting
the indium oxide-based transparent conductive film, as the base,
was attained. Compositions thereof are shown in Table 4. As
characteristics evaluation of the transparent conductive film
laminated bodies prepared, evaluation of pole figure was also
performed by X-ray diffraction measurement, in addition to similar
items performed in the zinc oxide-based transparent conductive
films of Examples 1 to 3.
[0180] In Table 4, characteristics evaluation results of the
transparent conductive film laminated bodies are shown. Any of the
transparent conductive film laminated bodies had nearly the same or
smaller surface resistance, as compared with the case of not
inserting the indium oxide-based transparent conductive film, as
the base, showing sufficient conductivity. As for surface roughness
Ra value and haze ratio of the laminated bodies, increasing
tendency was observed by inserting the base film, in Examples 56 to
59, however, they decreased significantly in Comparative Examples
41. Reason for decrease in the Ra value and haze ratio in
Comparative Examples 41 is that the base film was not a complete
crystalline film.
[0181] The transparent conductive film laminated bodies of Examples
56 to 59 showed sufficiently high values for utilizing as the
surface transparent electrode of the solar cell with superior
optical confinement effect. However, the transparent conductive
film laminated body of Comparative Examples 41 cannot be utilized
for that object, because of having small haze ratio.
Examples 60 to 63 and Comparative Example 42
[0182] The transparent conductive film laminated bodies were
prepared by using a zirconium-containing indium oxide-based
transparent conductive film, as the base, and forming the zinc
oxide-based transparent conductive film thereon. The indium
oxide-based transparent conductive film of the base, was prepared
by the following condition.
[0183] As shown in Table 4, target composition in preparing the
indium oxide-based transparent conductive film was changed within a
range of 0.25 to 7.05% by atom as Zr/(In+Zr). As film formation
condition as shown in Table 4, film formation gas pressure was set
at 0.2 Pa, argon gas mixed with 6% by volume of oxygen was used as
film formation gas, a direct current power of 400 W was input, and
annealing was performed at 400.degree. C. for 60 minutes in vacuum,
after film formation without heating the substrate. Composition of
the base films obtained by this method was nearly equal to the
target composition in any case. As for crystallinity of the film,
in the case of Zr/(In+Zr) is 7.05% by atom (Comparative Example
42), it was a mixed film of crystalline and amorphous substances,
but in the case where it is 0.25 to 6.50% by atom (Examples 60 to
63), it was a completely crystalline film. On this base film with a
film thickness of 300 nm, prepared in this way, the zinc
oxide-based transparent conductive film was formed similarly as in
Example 2. As for film formation speed of the zinc oxide-based
transparent conductive film, nearly the same high film formation
speed as in not inserting the indium oxide-based transparent
conductive film, as the base, was attained. Compositions thereof
are shown in Table 4. As characteristics evaluation of the
transparent conductive film laminated bodies prepared, evaluation
of pole figure was also performed by X-ray diffraction measurement,
in addition to similar items performed in the zinc oxide-based
transparent conductive films of Examples 1 to 3.
[0184] In Table 4, characteristics evaluation results of the
transparent conductive film laminated bodies are shown. Any of the
transparent conductive film laminated bodies had nearly the same or
smaller surface resistance, as compared with the case of not
inserting the indium oxide-based transparent conductive film, as
the base, showing sufficient conductivity. As for surface roughness
Ra value and haze ratio of the laminated bodies, increasing
tendency was observed by inserting the base film, in Examples 60 to
63, however, they decreased significantly in Comparative Examples
42. Reason for decrease in the Ra value and haze ratio in
Comparative Examples 42 is that the base film was not a complete
crystalline film.
[0185] The transparent conductive film laminated bodies of Examples
60 to 63 showed sufficiently high values for utilizing as the
surface transparent electrode of the solar cell with superior
optical confinement effect. However, the transparent conductive
film laminated body of Comparative Examples 42 cannot be utilized
for that object, because of having small haze ratio.
Examples 64 to 67 and Comparative Example 43
[0186] The transparent conductive film laminated bodies were
prepared by using a molybdenum-containing indium oxide-based
transparent conductive film, as the base, and forming the zinc
oxide-based transparent conductive film thereon. The indium
oxide-based transparent conductive film of the base, was prepared
by the following condition.
[0187] As shown in Table 4, target composition in preparing the
indium oxide-based transparent conductive film was changed within a
range of 0.25 to 7.50% by atom as Mo/(In+Mo). As film formation
condition as shown in Table 4, film formation gas pressure was set
at 0.3 Pa, argon gas mixed with 7% by volume of oxygen was used as
film formation gas, a direct current power of 400 W was input, and
annealing was performed at 300.degree. C. for 30 minutes in vacuum,
after film formation without heating the substrate. Composition of
the base films obtained by this method was nearly equal to the
target composition in any case. As for crystallinity of the film,
in the case of Mo/(In+Mo) is 7.50% by atom (Comparative Example
43), it was a mixed film of crystalline and amorphous substances,
but in the case where it is 0.25 to 6.85% by atom (Examples 64 to
67), it was a completely crystalline film. On this base film with a
film thickness of 180 nm, prepared in this way, the zinc
oxide-based transparent conductive film was formed similarly as in
Example 11. As for film formation speed of the zinc oxide-based
transparent conductive film, nearly the same high film formation
speed as in not inserting the indium oxide-based transparent
conductive film, as the base, was attained. Compositions thereof
are shown in Table 4. As characteristics evaluation of the
transparent conductive film laminated bodies prepared, evaluation
of pole figure was also performed by X-ray diffraction measurement,
in addition to similar items performed in the zinc oxide-based
transparent conductive films of Examples 1 to 3.
[0188] In Table 4, characteristics evaluation results of the
transparent conductive film laminated bodies are shown. Any of the
transparent conductive film laminated bodies had nearly the same or
smaller surface resistance, as compared with the case of not
inserting the indium oxide-based transparent conductive film, as
the base, showing sufficient conductivity. As for surface roughness
Ra value and haze ratio of the laminated bodies, increasing
tendency was observed by inserting the base film, in Examples 64 to
67, however, they decreased significantly in Comparative Examples
43. Reason for decrease in the Ra value and haze ratio in
Comparative Examples 43 is that the base film was not a complete
crystalline film.
[0189] The transparent conductive film laminated bodies of Examples
64 to 67 showed sufficiently high values for utilizing as the
surface transparent electrode of the solar cell with superior
optical confinement effect. However, the transparent conductive
film laminated body of Comparative Examples 43 cannot be utilized
for that object, because of having small haze ratio.
TABLE-US-00001 TABLE 1 Production condition of zinc-oxide based
transparent conductive film Characteristics of zinc-oxide based
transparent conductive film Input Surface Target composition power
Film formation Target composition Film Surface Haze Irregularity
Al/(Zn + Al) Ga/(Zn + Ga) Gas pressure Gas Type density speed
Substrate Al/(Zn + Al) Ga/(Zn + Ga) thickness resistance ratio Ra %
by atom % by atom (Pa) (Ar/O2) (W/cm2) (nm/min) (.degree. C.) % by
atom % by atom (nm) (.OMEGA./.quadrature.) (%) (nm) Remark Com.
Expl. 1 1.59 0 3 100/0 2.21 66.8 400 1.6 0 835 13.5 0.9 25.6 Com.
Expl. 2 0.8 0 68.1 0.83 0 826 34.9 1.2 24.5 Expl. 1 0.65 0 68.6
0.66 0 835 43.6 8.4 35.2 Expl. 2 0.43 0 69.5 0.46 0 845 46.9 11.4
49.2 Expl. 3 0.3 0 69.8 0.32 0 832 63.2 12.5 56.1 Com. Expl. 3 0.2
0 70.1 0.21 0 846 189.2 13.6 58.9 Com. Expl. 4 0 3.48 8 100/0 2.21
70.5 300 0 3.49 796 15.4 0.9 25.4 Com. Expl. 5 0 2.62 70.8 0 2.65
795 13.5 2.6 30.5 Expl. 4 0 1.74 71.1 0 1.78 788 11.5 10.8 48.5
Expl. 5 0 0.87 71.3 0 0.89 784 18.9 11.4 50.1 Expl. 6 0 0.3 71.5 0
0.31 781 24.5 12.1 56.3 Com. Expl. 6 0 0.2 71.8 0 0.2 785 158.3
13.5 59.6 Com. Expl. 7 1.96 1.96 5 100/0 2.21 66.8 350 1.97 1.97
831 14.5 0.9 25.4 Com. Expl. 8 0.38 0.95 68.1 0.39 0.98 823 24.5
2.6 30.5 Expl. 7 0.33 0.87 68.9 0.33 0.87 835 29.3 8.5 37.8 Expl. 8
0.49 0.49 68.6 0.49 0.49 824 35.6 10.1 45.2 Expl. 9 0.28 0.28 68.6
0.29 0.29 832 41.5 11.1 46.8 Expl. 10 0.15 0.15 69.1 0.16 0.16 851
56.4 12.1 49.5 Com. Expl. 9 0.1 0.1 69.5 0.11 0.11 835 178.5 12.8
51.1 Com. Expl. 10 3.16 0 3 100/0 0.442 7.1 350 3.18 0 821 36.5
12.5 42.5 NON-PATENT LITERATURE 2 Com. Expl. 11 1.105 25.1 835 16.5
2 33.7 Com. Expl. 12 1.66 42.3 815 12.5 0.9 24.5 Com. Expl. 13 2.21
65.5 823 11.1 0.7 21.5 Com. Expl. 14 0 4.99 8.3 100/0 0.442 8.2 400
0 5.03 795 90.4 0.9 24.4 Com. Expl. 15 1.105 27.5 791 36.9 0.4 19.1
Com. Expl. 16 1.66 44.1 786 22.5 0.2 18.5 Com. Expl. 17 2.21 69.5
785 18.5 0.2 18.1 Com. Expl. 18 0 1.31 5.5 100/0 2.76 90.5 350 0
1.35 830 16.2 5.2 33.3 Expl. 11 90.9 1010 12.9 8.6 37.1 Expl. 12
90.4 1350 10.9 11.6 49.5 Expl. 13 90.5 1620 7.7 13.2 55.2 Com.
Expl. 19 0.28 0.28 1 100/0 1.66 41.2 300 0.29 0.29 1340 16.8 4.6
31.5 Expl. 14 2 42.3 1360 24.5 8.9 36.8 Expl. 15 10.5 44.5 1355
26.3 11.5 46.2 Expl. 16 15 43.5 1350 29.6 13.5 55.5 Com. Expl. 20
20 35.2 1352 75.2 16.8 65.3 Weak film adhesion Com. Expl. 21 0 0.3
6 100/0 2.76 75.2 150 0 0.31 1005 15.6 2.3 30.9 Expl. 17 72.3 200
1012 19.1 8.2 37.5 Expl. 18 71.8 400 1008 20.1 15.2 63.2 Expl. 19
68.5 500 1010 56.3 18.5 65.3 Com. Expl. 22 35.6 600 1005 78.5 19.5
69.8
TABLE-US-00002 TABLE 2 Production condition of zinc oxide-based
transparent Characteristics of zinc conductive film oxide-based
transparent Zinc oxide-based Characteristics of laminated body
Aneal conductive film transparent conductive Inclination of Target
Input condition Film film formed at the c-axis of zinc composition
Gas Ar/O2 power Substrate after composition Film surface of indium
Surface Haze Surface oxide-based Sn/(In + Sn) pressure (% by
density temperature film Sn/(In + Sn) thickness oxide-based
transparent resistance ratio roughness transparent % by atom (Pa)
volume) (W/cm2) (.degree. C.) formation % by atom Crystallinity
(nm) conductive film (.OMEGA./.quadrature.) (%) Ra (nm) conductive
film Com. Expl. 23 9.29 0.6 94/6 1.660 300 Non 9.31 Crystalline 150
Com. Expl. 2 11.5 1.1 24.0 15 Expl. 20 film Expl. 1 13.4 8.1 33.2
13 Expl. 21 Expl. 3 15.0 11.1 49.5 14 Com. Expl. 24 Com. Expl. 3
110.2 12.1 54.6 13 Expl. 22 Expl. 4 9.1 9.5 43.2 13 Expl. 23 Expl.
6 15.0 11.1 49.9 14 Com. Expl. 25 Com. Expl. 8 9.5 2.0 30.1 12
Expl. 24 Expl. 7 10.5 8.1 35.4 13 Expl. 25 Expl. 9 13.2 10.2 46.9
12 Expl. 26 Expl. 10 14.8 10.9 46.5 13 Com. Expl. 26 Com. Expl. 9
102.1 11.0 48.5 12 Com. Expl. 27 9.29 0.6 94/6 1.660 RT 400.degree.
C., 9.31 150 Com. Expl. 2 12.2 1.2 23.5 5 Expl. 27 30 min Expl. 1
14.2 11.2 46.5 8 Expl. 28 in Expl. 3 15.8 14.1 55.8 6 Com. Expl. 28
vacuum Com. Expl. 3 125.0 15.2 64.5 4 Com. Expl. 29 300.degree. C.,
9.32 Com. Expl. 5 10.5 2.9 31.2 3 Expl. 29 30 min Expl. 4 9.8 13.2
53.1 3 Expl. 30 in Expl. 6 15.5 13.8 54.2 5 Com. Expl. 30 vacuum
Com. Expl. 6 95.2 15.2 63.3 4 Expl. 31 350.degree. C., 9.31 Expl. 7
11.0 9.6 42.1 1 Expl. 32 30 min Expl. 9 13.5 12.5 56.5 6 Expl. 33
in Expl. 10 15.0 14.2 58.2 2 vacuum Com. Expl. 31 17.56 0.3 92/8
2.210 RT 200.degree. C., 18.10 Cryst. + Amor. 45 Expl. 17 19.0 5.2
24.0 8 Expl. 34 14.95 30 min 14.98 Crystalline 20.5 9.2 37.1 6
Expl. 35 9.29 in 9.32 film 15.2 9.5 37.8 5 Expl. 36 4.62 vacuum
4.65 14.5 8.9 37.5 4 Expl. 37 0.20 0.21 15.2 9.2 37.0 1
TABLE-US-00003 TABLE 3 Characteristics of laminated body Production
condition of indium oxide-based transparent Znc oxide-based
Inclination conductive film Characteristics of zinc oxide-based
transparent conductive of c-axis of Aneal transparent conductive
film film formed at the zinc oxide- Target Charge condition Film
surface of indium based composition Gas Ar/O2 power Substrate after
composition Film oxide-based Surface Surface transparent Ti/(In +
Ti) pressure (% by density temperature film Ti/(In + Ti) thickness
transparent conductive resistance Haze ratio roughness conductive %
by atom (Pa) volume) (W/cm2) (.degree. C.) formation % by atom
Crystallinity (nm) film (.OMEGA./.quadrature.) (%) Ra (nm) film
Com. Expl. 32 1.73 0.4 94/6 1660 300 Non 1.79 Crystalline film 200
Com. Expl. 2 8.5 1.1 24.0 13 Expl. 38 Expl. 1 9.1 8.2 33.1 11 Expl.
39 Expl. 3 9.6 11.5 50.1 12 Com. Expl. 33 Com. Expl. 3 78.5 12.1
54.6 14 Expl. 40 Expl. 4 8.8 10.1 44.8 12 Expl. 41 Expl. 6 13.5
10.8 45.2 13 Com. Expl. 34 Com. Expl. 8 9.1 2.1 31.1 15 Expl. 42
Expl. 7 9.1 8.2 35.2 12 Expl. 43 Expl. 9 9.9 10.5 47.5 13 Expl. 44
Expl. 10 10.5 11.2 46.5 11 Com. Expl. 35 Com. Expl. 9 89.5 12.1
49.1 12 Com. Expl. 36 1.73 0.4 94/6 1660 RT 400.degree. C., 1.76
200 Com. Expl. 2 9.1 2.5 30.1 5 Expl. 45 30 min Expl. 1 9.8 15.6
63.2 6 Expl. 46 in Expl. 3 10.1 16.9 65.2 4 Com. Expl. 37 vacuum
Com. Expl. 3 79.5 18.2 65.2 3 Com. Expl. 38 300.degree. C., 1.77
Com. Expl. 5 9.8 3.2 31.6 1 Expl. 47 30 min Expl. 4 9.1 14.1 60.2 2
Expl. 48 in Expl. 6 14.2 15.1 63.1 3 Com. Expl. 39 vacuum Com.
Expl. 6 85.9 16.5 65.0 5 Expl. 49 350.degree. C., 1.75 Expl. 7 8.9
10.1 44.8 0 Expl. 50 30 min Expl. 9 10.5 15.2 64.2 3 Expl. 51 in
Expl. 10 11.5 14.5 57.6 1 vacuum Com. Expl. 40 7.25 0.3 93/7 2210
RT 300.degree. C., 7.35 Cryst + Amor. 100 Expl. 14 24.8 5.0 31.0 2
Expl. 52 5.50 30 min 5.58 Crystalline 13.5 12.5 52.5 1 Expl. 53
3.47 in 3.49 film 8.9 13.1 55.1 0 Expl. 54 0.88 vacuum 0.91 9.5
12.8 51.6 3 Expl. 55 0.35 0.37 12.5 13.3 55.3 2
TABLE-US-00004 TABLE 4 Production condition of indium oxide-based
transparent Characteristics of zinc oxide-based Target Charge Aneal
Film composition Gas Ar/O2 power Substrate condition composition
Film W/(In + W) pressure (% by density temperature after film W/(In
+ W) % thickness % by atom (Pa) volume) (W/cm2) (.degree. C.)
formation by atom Crystallinity (nm) Com. Expl. 41 5.01 0.3 93/7
2.210 RT 300.degree. C., 5.05 Cryst./amor. 180 Expl. 56 4.28 30 min
4.28 Crystalline Expl. 57 3.06 in 3.06 film Expl. 58 1.00 vacuum
0.91 Expl. 59 0.30 0.37 Com. Expl. 42 7.05 0.2 94/6 2.210 RT
400.degree. C., 7.08 Cryst./amor. 300 Expl. 60 6.50 30 min 6.56
Crystalline Expl. 61 3.50 in 3.55 film Expl. 62 0.65 vacuum 0.68
Expl. 63 0.25 0.27 Com. Expl. 43 7.50 0.3 93/7 2.210 RT 350.degree.
C., 7.58 Cryst./amor. 180 Expl. 64 6.85 30 min 6.91 Crystalline
Expl. 65 4.50 in 4.85 film Expl. 66 2.56 vacuum 2.60 Expl. 67 0.25
0.26 Znc oxide-based transparent conductive film formed at the
Characteristics of laminated body surface of indium Inclination of
oxide-based Surface c-axis of zinc oxide- transparent Surface
resistance roughness based transparent conductive film
(.OMEGA./.quadrature.) Haze ratio (%) Ra (nm) conductive film Com.
Expl. 41 Expl. 6 24.6 7.5 33.2 2 Expl. 56 12.4 13.5 55.3 3 Expl. 57
10.2 14.5 60.2 2 Expl. 58 8.9 15.1 64.2 2 Expl. 59 12.8 17.8 62.5 2
Com. Expl. 42 Expl. 2 20.5 7.1 30.5 3 Expl. 60 15.2 13.5 58.5 4
Expl. 61 11.2 12.8 56.5 6 Expl. 62 9.3 13.8 58.6 1 Expl. 63 10.6
14.5 61.5 9 Com. Expl. 43 Expl. 11 12.2 6.8 33.8 8 Expl. 64 9.5
12.5 55.2 2 Expl. 65 8.5 13.2 56.8 6 Expl. 66 9.1 14.1 58.6 4 Expl.
67 10.1 13.8 56.8 5
[0190] The silicon-based thin film solar cell of the present
invention adopts the transparent conductive film superior in
hydrogen reduction resistance and also superior in optical
confinement effect, and the transparent conductive film laminated
body using the same, therefore it is a solar cell with high
photoelectric conversion efficiency. The transparent conductive
film having high conductivity and high transmittance in a visible
light region has been utilized in an electrode or the like, for a
solar cell or a liquid crystal display element, and other various
light receiving elements, as well as a heat ray reflection film for
an automotive window or construction use, an antistatic film, and a
transparent heat generator for various anti-fogging for a
refrigerator showcase and the like.
* * * * *